PDF/X in a Nutshell PDF for printing – The ISO standard

Dietrich von Seggern Peter De Bruyne Andrew Bailes-Collins Stephan Jaeggi

■■ The history of PDF/X

■■ PDF/X: The key facts

■■ Technical side and requirements of PDF/X

■■ Users and industry segments

■■ Tools and usage

■■ PDF/X-Plus

■■ PDF/X and the other PDF standards PDF/X in a Nutshell PDF for printing – The ISO standard This work, including all its component parts, is copyright protected. All rights based thereupon are reserved, including those of translation, reprinting, presentation, extraction of illustrations or tables, broadcasting, microfilming or reproduction by any other means, or storage in any data-processing device, in whole or in part. Reproduction of this work or any part of this work is only permitted where legally specified in the Copyright Act of the Federal Republic of Germany dated the 9th of September 1965.

© 2017 Association for Digital Document Standards e. V., Berlin [email protected] Produced in Germany

The use of any names, trade names, trade descriptions etc. in this work, even those not specially identified as such, does not justify the assumption that these names are free according to trademark protection law and thus usable by anyone. Text: PDF Association Layout, cover design, design and composition: Alexandra Oettler Cover image: Tomasz Pacyna, Dreamstime.com

Contents

Introduction: The history of PDF/X 5 PDF/X: Tools and usage 12 Adobe introduces PDF PDF/X Tools Prepress became digital and open PDF/X Creation PDF changed the prepress world PDF/X Conformance and Correction Standardizing PDF for print Desktop solutions Server-based solutions PDF workflow and output PDF/X: The key facts 6 Programming libraries What’s not in PDF/X Further quality requirements: PDF/X-Plus 14 Technical side and requirements of PDF/X 7 Ghent (PDF) Workgroup PDF/X-1a: Complete exchange PDFX-ready in Switzerland PDF/X-3: Color management PDF/X-2: Partial exchange PDF/X-4: Transparency PDF/X and the other PDF standards 16 PDF/X-5: More flexibility PDF PDF/X-6: Building on PDF 2.0 PDF/A (ISO 19005) PDF/E (ISO 24517) PDF/VT (ISO 16612-2) PDF/X: Users/industry segments 9 PDF/UA (ISO 14289) Designers, creators and advertising agencies Magazines and newspapers Commercial print and digital printing Large format printing Labels and packaging printing

PDF/APDF/X in a Nutshell 2.0 III Introduction Introduction: The history of PDF/X by Dietrich von Seggern

PDF/X was the first ISO standard companies, and generated a need for PDF’s inherent flexibility made it based on PDF technology. A subset of exchanging print layouts between clear that not every PDF file could be the PDF specification, PDF/X was de- companies. used for printing, a fact that triggered signed to constrain PDF files in order to At that time, I was working for the developers to create preflight tools cater to specific use-cases. The first part, German newspaper marketing orga- to establish whether a given PDF file PDF/X-1a, based on PDF 1.3, came out nization responsible for a network met the requirements of the printing in 2001. Why did that happen? connecting advertising agencies with industry. newspaper production facilities. EPS Adobe introduces PDF (Encapsulated PostScript) was used Standardizing PDF for print In the 1980s, Adobe invented Post- as the exchange format. It was – com- To streamline their own workflows, Script, a standard page description pared to PDF – huge, no viewers were printers started to develop their own language that allowed for connecting available, it was not easy to parse and requirements for PDF files, and they any (PostScript) printer to any (Post- preflight, fonts were usually not em- shared these requirements with the Script) layout application / computer. bedded and had to be sent separately, creators of the PDF files that they PostScript serialized page description and so on. had to process and print. commands so that a printing device Due to the limitations of EPS, we Technically this made a lot of sense, could convert them into a printed were constantly searching for a re- but this approach had some major lim- page without big processors or lots of placement. Unfortunately, all candi- itations: First, it required that a print memory; at that time, a very import- dates (there was PDF 1.0 but also a file creator had to align their PDF files ant requirement. However, PostScript few others) were too focused on doc- with the print house of choice, which was not designed to be saved to a disk, ument processes and did not support meant that a PDF file acceptable to it usually resulted in very large files the print color space with CMYK one print house might be refused by and on screen rendering was – if at all and many other core requirements another. Discussing the print house’s possible – time consuming. of prepress. When Adobe announced specific requirements, which might be As the developer of Photo- PDF 1.2 – which would not only sup- necessary to alignment, represented shop, FrameMaker and Illustrator, port CMYK, but in addition create overhead, and didn’t scale well. Adobe had a strong graphic arts very small files even for high resolu- Even more important was the fact background. However, when they tion images – it sounded too good to that print file creators were usually designed PDF to overcome the be true. also the printer’s customers or at least shortcomings of PostScript they closely affiliated with them. They dis- initially thought of it more as an ex- PDF changed the prepress world covered that it is difficult to apply strict change format for documents. What PDF 1.2 was a great step forward, but rules that potentially require addition- Adobe did not see – at least not in there were still a few weaknesses and al work to an input when the supplier is the beginning – was the desperate particularly one important shortcom- at the same time the customer. What’s need for a data exchange format in ing: the lack of spot color support. more likely that the customer just goes the print industry as well. PDF’s ability to change the whole pre- elsewhere to find a printer that con- press production chain was nonethe- forms to the customer’s preferences Prepress became digital and open less becoming clear. In 1998, a group rather than being forced to match pref- In the 1990s, the print production of European prepress experts wrote erences with the print vendor. marketplace was disrupted by desk- a white-paper on “PDF for prepress” It was clear that what was needed top publishing technologies bring- and sent it to Adobe; almost all of this was a clear 3rd party specification – a ing what used to be very expensive group’s recommendations were ad- standard – for both creator and receiv- tools to the average user’s desktop. dressed in PDF 1.3. From that point er. This urgent need for independent This change affected the cost and forwards PDF was a cornerstone of rules for print-ready PDF culminated equipment used by print production graphic arts workflows. in the development of PDF/X.

PDF/APDF/X in a Nutshell 2.0 5 The key facts PDF/X: by Dietrich von Seggern The key facts

nate color must be the same for all oc- PDF/X is a subset of PDF – see “Tech- currences of the respective spot color. nical side and requirements of PDF/X”, page 7, for an overview. As such, con- ■■Fonts must be embedded (either fully forming with PDF/X means accepting embedded, or as an embedded subset specific requirements and restrictions to in which all characters used in the text the use of the PDF format. are present). One principle of PDF/X is that con- ■■Images must be present in the PDF forming files must be complete, i.e. fully (no external graphical content is al- self-contained. In addition, nothing may lowed). PDF/X has to be complete and appear on a PDF/X page that is either not everything on a PDF page has printable at all (such as video or 3D) or ■■No password protection of any type. to be printable. where print output is not fully defined ■■No transfer curves (since they modify (for example, if a font is not embed- appearance of colors). ded). While the first rule is rather easy to implement, the latter is more difficult. ■■No alternate images (e.g. no low-reso- PDF allows for many complex situations, lution alternates). for example, colors in semi-transparent ■■If the bleed zone is defined, the Bleed- overlapping objects. In other cases, it may Box must be outside the printable area not be clear whether objects on a layer (the TrimBox). are to be printed. There are many other ■ cases of interdependencies in which it is ■No use of LZW compression. difficult to determine whether the print ■■No annotations in the print area. result is unambiguously defined, or not. ■ Certain features needed only for some ■No audio, video or 3D annotations. print applications (e.g., a bleed zone) are ■■No form fields or JavaScript. not required in PDF/X as they are not ■■No embedded files. required in all print products. Wher­ever it makes sense in such cases, however, ■■PDF metadata must indicate whether PDF/X requires that if such information the PDF has been trapped, or not. is present, it must be accurate. PDF/X re- ■■PDF metadata must claim confor- quires, for example, that if a bleed zone mance to PDF/X and to which part is defined then that zone must not be en- and conformance level of the PDF/X closed by the trimmed print product. standard. Core principles of PDF/X What’s not in PDF/X These requirements apply in all parts and PDF/X does not include provisions that conformance levels of PDF/X. although important, may vary depend- ■■An Output Intent must be present that ing on the printing conditions, e.g. the uses an ICC profile to specify the in- minimum image resolution or the bleed tended printing conditions (print de- zone. vice type, paper type) when colors (or Other non-ISO standards have been de- shades of gray) are defined. veloped based on PDF/X that cover such production specific requirements (see ■ ■Spot colors may only be used if they “Further quality requirements: PDF/X- have an alternate color, and this alter- Plus”, page 14, for further information).

6 PDF/APDF/X in a in Nutshell a Nutshell 2.0 Technical side Technical side and requirements of PDF/X by Peter De Bruyne

Even as the first part of PDF/X was PDF/X-3: Color management published as ISO 15930-1 in 2001, PDF/X-3, originally published in 2002, others were already in development. shares most of its requirements with PDF/X rapidly expanded into a fami- PDF/X-1a, but it lifts the restriction to ly of standards supporting a wide va- CMYK and spot colors. In PDF/X-3, riety of print production workflows. graphics can use CMYK, greyscale, Each part of PDF/X builds on a pre- RGB, Lab and ICC based color spaces. vious part, providing flexibility while It requires, however, that device color ensuring reliable exchange, the core spaces may be used only if the same ­rationale for PDF/X. color space is used for the ICC profile in the Output Intent, so DeviceRGB re- PDF/X-1a: Complete exchange quires the Output Intent to use an RGB PDF/X-1a was the first and most re- ICC profile. Since this is usually not PDF/X soon expanded into a strictive member of the PDF/X fam- the case, as a practical matter, only ICC family of standards, support- ily. PDF/X-1a aims for “complete based RGB or CalRGB are permitted. ing a wide variety of work- exchange”; a single file must contain Accordingly, the faithful reproduction flows. all information needed for print- of PDF/X-3 documents requires a col- ing the document as intended by the or managed workflow. sender. The core principles are the same as in all PDF/X-2: Partial exchange PDF/X standard parts: all fonts must be The strict requirement of including all embedded and external data, password resources inside a single file is not ap- protection, visible annotations and Ja- propriate for every workflow. PDF/X-2 vaScript are not allowed (see “PDF/X: addresses this need; it allows the use The key facts”, page .6 Other require- of proxy elements referencing external ments are specific to PDF/X-1a, e.g. graphics. Otherwise, PDF/X-2 is the those pertaining to transparency and same as PDF/X-3, so it allows ­col­or layers which later (in PDF/X-4, see be- managed elements next to spot ­colors low) are permitted. and device colors prepared for the Additionally, printing a PDF/X-1a specified output intent. file must be possible without requir- ing prior color correction. Therefore, PDF/X-4: Transparency print elements can only use CMYK, The previous PDF/X variants do not greyscale or spot colors; no RGB or support the features of more modern device-independent color spaces are (beyond PDF 1.4) versions of PDF. By permitted. 2008, it was time to bring PDF/X up to This implies that CMYK or grey- date with current PDF specifications. scale elements must have been pre- PDF/X-4 is based on PDF 1.6, pub- pared for the intended output process lished in 2004. This specification as specified in an Output Intent, which added support for new features, in- consists largely of an ICC profile char- cluding layers, JPEG2000, OpenType acterizing the intended print process. fonts, and 16-bit images. In addition, The use of standard Output Intents PDF/X-4 allows the use of transpar- facilitates the standardized data ex- ency, a PDF 1.4 feature forbidden in change that is the objective of PDF/X. PDF/X until PDF/X-4. →

PDF/APDF/X in a Nutshell 2.0 7 Technical side

PDF/X-4 includes two variations any such case an n-colorant ICC pro- known as “conformance levels”: PDF/X-4 file must be specified in the Output and PDF/X-4p. Intent; it can either be referenced as in PDF/X-4p, or as an embedded file. ■ PDF/X-4 inherits the rules of PDF/X-3 for complete exchange in color man- ■ PDF/X-5g extends the PDF/X-4 stan- aged workflows, with the requirement dard with the ability to use external of always embedding the output intent raster and vector graphics. Like the ICC profile. older PDF/X-2, a PDF/X-5g file can contain temporary placeholders that ■ PDF/X-4p provides a form of partial reference an external resource. exchange; it allows the ICC profile to be maintained externally. This ensures ■ PDF/X-5pg takes PDF/X-5g one step better efficiency in workflows where further. It offers the same method for many files share the same output in- external graphics as PDF/X-5g, and tent, or where embedding the ICC combines it with the PDF/X-4p’s op- profile would substantially increase tion of the output intent referenced as the file size. an external ICC profile. PDF/X-5: More flexibility PDF/X-6: Building on PDF 2.0 PDF/X-5 is a set of three conformance PDF/X-6 is currently under development levels, all geared towards different work- within the ISO committee that manages flows. Each conformance level expands the PDF/X specification. PDF/X-6 will re- on PDF/X-4 or PDF/X-4p. lax some requirements, but the main dif- ference as compared to previous PDF/X ■ PDF/X-5n allows for n-colorant color standards is that it will be based on ISO spaces that are used where the tra- 32000-2, better known as PDF 2.0. ditional four print process colors New to PDF 2.0 are page level Out- (CMYK) are not enough. n-colorant put Intents and better support for color spaces may be required to enable multi channel print color spaces a larger color gamut (e.g. CMYK plus (more channels than just CMYK) as is Green, Violet, Orange) to allow for increasingly used in packaging or on more accurate skin tones, pastel colors digital printing devices. Annotations or the like. Another use of PDF/X-5n may be used within the print area if is in packaging, in which certain they have a printable appearance that product-specific spot colors are also complies with the same requirements as used for imagery as process colors. In any other page content.

8 PDF/APDF/Xin ain Nutshell a Nutshell 2.0 User segments PDF/X: Users/industry segments by Andrew Bailes-Collins

Where do all these different flavors of PDF/X file is just a matter of selecting PDF/X fit, and for anybody wanting to the required PDF/X version, and en- use PDF/X, which versions should they suring the file is compliant after cre- investigate? ation. For those considering moving to a If an artwork creator supplies a con- PDF/X-based workflow it’s critical that forming PDF/X file, then any print the chosen PDF/X version fits the capa- service provider should have the tools bilities and objectives of that workflow. and knowledge to be able to process If the workflow and output RIP are rel- and print that file without problems, atively modern (purchased within the the key rationale and value proposition last 3-4 years), it will almost certainly that ­underpins the PDF/X standards. be able to work with the latest PDF functionality such as live transparency Magazines and newspapers and layers. In this situation, PDF/X-4 Magazines and newspapers often inte- is highly recommended. grate content produced elsewhere (e.g., In an older workflow system that has advertising) into their products. Typi- difficulty digesting some of the newer cally, these publishers produce very de- PDF functionality such as transpar- tailed specifications on how a PDF file ency, it’s probably not a good idea to should be created and checked before attempt adopting PDF/X-4; an older they receive it. Due to the sheer volume What is most important for PDF/X version is probably more suit- of content they receive and deliver, and anybody who wants to move to able. the deadlines they work to, they nor- a PDF/X based workflow, is that It’s important to leverage the free mally expect any incoming advertising the PDF/X version they use fits dedicated test suites that allow users to files to be correct when delivered. their workflow and the capa- evaluate their workflow for PDF/X-4 The production for these types of bilities of that workflow. readiness; the Ghent PDF Workgroup publications is split into two distinct (GWG) Output Suite is one such. areas, receiving files for advertising, When testing, all applications within­ and delivering final pages for print. a workflow must be considered, in- cluding (but not limited to): imposi- ■■Receiving: PDF files of advertising tion software, color servers, ink saving content are received from external sup- software, trapping software, and out- pliers; these files are checked and then put RIPs. incorporated with editorial content in a layout application to create the final Designers, creators and advertising pages of the publication. agencies The benefit for a design company in ■■Delivering: The completed publica- working with PDF/X is that it’s easier tion is exported as a PDF file and sent than coping with a myriad of PDF cre- to a print site. ation settings from different printing companies and suppliers. Since smooth workflows is of critical The output settings needed to create interest to these businesses, magazines valid PDF/X files are pre-configured and newspapers were among the very into most professional page layout and early adopters of PDF/X. New York’s design applications, so generating a Time Inc. is credited with the first

PDF/APDF/X in a Nutshell 2.0 9 User segments

known use of a PDF/X-1 file in live of handling it correctly. In many cas- production, when they ran an adver- es, their output devices were based on tisement for Bayer in the March 13, PostScript, so files with transparency 2000 issue of TIME magazine. needed to be flattened prior to out- Today, most newspapers and maga- put to ensure correct results and avoid zine publishers have joined Time, Inc. waste and spoilage. in adopting PDF/X. Most of these busi- In today’s commercial and digi- If you have a modern work- nesses require all advertising to be de- tal printing marketplace, however, flow and output rip, then you livered as a PDF/X-1a file, and in turn PDF/X-4 is very much in use. If you are more than capable of han- deliver their final pages to the printer have a modern workflow and output dling a PDF/X-4 file. as PDF/X-1a files. RIP, then you are more than capable of It’s fair to ask: why haven’t periodical handling a PDF/X-4 file. publishers embraced the newer ver- One aspect of PDF/X-4 that often sions of PDF/X, such as PDF/X-4? The causes concern, particularly in sheet- ­answer is straightforward; their current fed and web offset, is the fact that color workflows are working predictably and spaces such as RGB and Lab are allowed. correctly. Another limitation is the fact Many printers are not confident in han- that as yet, many suppliers and stake- dling files that contain these color spac- holders in the production chain are es, and prefer to handle only CMYK currently unwilling to accept responsi- and spot color based files. It is, however, bility for flattening transparencies, and perfectly possible to use PDF/X-4 based handling other PDF/X-4 functionality. preflight configurations that forbid Until recently, to these publishers, the these color spaces (i.e., permitting only risks in handling the latest versions of a subset of PDF/X-4). The newer GWG PDF/X has not been worth the bene- preflight specifications (see“Further fits of making the transition, but this is quality requirements: PDF/X-Plus”, page now changing. 14, are all based on PDF/X-4. A key driver for this change is that In digital printing, particularly with PDF/X-1a files are not very useful output engines that have large color when it comes to re-purposing con- gamuts, RGB based files are beneficial, tent. However, newspaper and mag- as they can use the full color gamut azine publishers increasingly need to available in the press rather than con- develop cross-media content that’s straining the color gamut to that of a optimized for tablet or online publica- conventional CMYK based process. tion. This requirement, along with the gradual acceptance of modern produc- Large format printing tion techniques, is driving the newspa- PDF/X-1a, PDF/X-3 and PDF/X-4 are per and magazine publishing industry all relevant to large format printing, towards PDF/X-4. but there are certain aspects of each that should be recognized. The choice Commercial print and digital printing of format will depend on the type of Commercial and digital printers work, the workflow and knowledge jumped on PDF/X-1a when it was re- of the printing company in question. leased. For many of these companies, These aspects are fundamentally the it is still the standard they use for the same as those discussed in the com- same reasons as the periodical publish- mercial print section above. ers discussed earlier: predictability and One attribute of a PDF file that can responsibility. be a requirement for large format When it was first released, live trans- printing is the ‘user unit’. A PDF file parency caused a major problem for (prior to PDF 2.0, which allows pages printing companies, as their output measurable in kilometers) has a tech- RIPs and workflows were not capable nical size limitation of 200 x 200 inch-

10 PDF/APDF/X in a in Nutshell a Nutshell 2.0 User segments es, which is fine for most commercial Labels and packaging printing printing, but when you want to print a Label and packaging differs from other poster that covers the side of a build- methods of print production for sever- ing, this limitation becomes an issue. al reasons. A key distinction is that the To overcome this size limitation the size of the final job is often not a square PDF 1.6 specification included a func- or a rectangle, so it cannot be defined tion called ‘UserUnit’ which effectively by a PDF page box. Additionally, in enables the size of the PDF to be scaled packaging, the use of multiple spot col- by a multiplication factor, allowing the or inks rather than just CMYK is very creation of larger page sizes. common, with spot colors frequently The PDF/X-4 specification is based used in image separations as well as in on PDF 1.6, so if it’s a requirement that text and vector graphics. PDF files are supplied at their correct Additionally, within modern pack- size, then PDF/X-4 would be needed. aging production, extended gamut However very often in this market, printing is becoming more prevalent, files are supplied at a smaller size than especially with digital devices. Extend- the final required size, and are enlarged ed gamut printing uses a fixed ink set on output. This is a more traditional of CMYK plus additional spot colors method of working, and has been the (orange, violet and green are typical) case since the days when film supplied to produce a very large color gamut, as a reduced size version would be pro- allowing a large range of spot colors to jected on a large camera to the correct be produced without the need to run final size. individual spot color inks. Digital large format devices very of- All PDF/X formats require that an ten have large multi-color ink sets to output intent is defined (see “Technical deliver a wide color gamut. Some de- side and requirements of PDF/X”, page vices have up to 12 inks to maximize 7 that uses an ICC profile to char- the quality of printing, and can pro- acterize the intended output. Output duce most available spot colors (ex- intents use normally CMYK ICC pro- cepting special inks such as metallic). files, but for PDF/X-4 or PDF/X-3 that The output RIPs on these devices of- can also be RGB or even Gray profiles. ten have very sophisticated color man- To fully support multi-channel work- agement functionality in order to work flows with PDF/X, a multi-channel with these ink sets, and it makes sense color profile is required. Multi-chan- that PDF files being printed should nel profiles are not supported by any of maximize this capability. In this case the previously mentioned PDF/X stan- PDF/X-3 or PDF/X-4 can be useful as dards. The only PDF/X version which they allow color-managed color spaces that allows for multi-channel profile such as Lab, CalRGB or use of an em- support is PDF/X-5n bedded ICC profile. As of this writing, PDF/X usage in When investigating PDF/X for large the label and packaging market is not format, a key consideration is the out- widespread, but with PDF 2.0 and the put RIP driving the printer. There are upcoming PDF/X-6, functionality will a large variety of different large format be added to make adoption easier and RIPs available, with different quality more beneficial. and functionality. Thorough testing is advisable to ensure the output of the re- quired PDF/X level is correct and pre- dictable, before implementing a PDF/X based workflow. The GWG output suite mentioned above usually proves to be very useful in such testing.

PDF/APDF/X in a Nutshell 2.0 11 Tools and usage PDF/X: by Andrew Bailes-Collins Tools and usage

PDF/X Tools The graphic arts industry uses a specif- The good news for anybody wishing to ic term for this quality control process: start working with PDF/X standards, preflight. The term was inherited from is that there are many tools available to the preflight checks that a pilot carries support all aspects of PDF/X produc- out before taking off in an aircraft. In a tion. The current PDF/X specifications similar process, a print service provider are well established and mature as far as will thoroughly check a PDF file before it software developers are concerned. enters the production process to ensure it is of sufficient quality for the required PDF/X Creation printed product. PDF/X files can be created directly from Most PDF preflight solutions offer the professional page layout packages such as opportunity for a Print Service Provider Adobe InDesign or Quark Xpress. When (PSP) to correct a lot of the issues that can Quality control and PDF/X con- exporting to PDF, the user can simply arise within PDF files. This can be done formance are an absolutely key select the required PDF/X version (1, 3, as part of the service the PSP provides part of the production process. or 4) and the software will guide the user, to its customer, or can be chargeable. In allowing only configuration settings that newspaper or magazine production, it is will produce a valid PDF/X file. not uncommon for publications to insist It is not possible to directly export a on a ‘print ready’ PDF/X file. These pub- valid PDF/X file using the output op- lications are not willing to take the re- tions within office applications such as sponsibility for any potential issues that Microsoft Word or OpenOffice. However, may arise if they correct the file them- it is possible to export a PDF file that can selves. then be converted to PDF/X using an ad- PDF/X preflight and correction solu- ditional application capable of correcting tions are available in several different the file to meet one of the PDF/X stan- types of application. dards. These solutions can be desktop or server-based, depending on the volume of Desktop solutions files that need to be processed. These solu- For users who have a relatively low tions generally begin by checking PDF/X number of files to process, a manual conformance, and subsequent correction ­application will probably be the most to PDF/X is part of this process. appropriate.­ Desktop applications such as Adobe PDF/X Conformance and Correction Acrobat have built–in preflight capabil- Quality control and PDF/X conformance ities that enable PDF/X conformance are a key part of the production process. to be checked and corrected. There are It doesn’t matter if you are supplying files also third-party plugin applications for to a print service provider, or processing Adobe Acrobat that extend those pre- PDF files within a print company; quali- flight and correction capabilities. ty control is paramount. Failure to ensure that a PDF file meets the required stan- Server-based solutions dard can result in missed deadlines, wast- For users who must check and correct ed time, material and extra cost. The later hundreds or thousands of PDF/X files a a problem with a PDF file is detected, the day, hot-folder driven and server-based more expensive that problem is to fix. preflight solutions are available. These

12 PDF/APDF/X in a in Nutshell a Nutshell 2.0 Tools and usage applications are often also available as configured appropriately to handle the Command Line Interface (CLI) software PDF/X version in use; it is not sufficient capable of driving the quality control to just use a PDF/X preflight check. Many process programmatically. These allow workflow vendors provide data sheets ex- high volume automated production, and plaining how workflows must be config- can be driven by external systems using ured to handle PDF/X files correctly. database connections or XML job tickets to allow the preflight check to be specif- Programming libraries ic to the customer’s order or advertising Programming libraries allow developers booking. to integrate PDF/X functionality into their own applications without having to PDF workflow and output develop the technology from scratch. PDF/X conformance and preflight are Some desktop or server-based prod- just two of the prepress production pro- ucts are also available as programming cesses that a PDF/X file must go through libraries. With these “Software Develop- to be successfully printed, but they are ment Kits”, companies can add PDF/X only pieces in a much larger workflow functionality with minimal effort, and puzzle. When working with PDF/X, it’s bring solutions to market very quick- important that all pieces and processes in ly. These libraries offer PDF/X creation, a print production workflow system are preflight and/or correction.

PDF/APDF/X in a Nutshell 2.0 13 PDF/X-Plus Further quality requirements: by Stephan Jaeggi PDF/X-Plus

PDF/X only defines the general require- ing and packaging workflows. Originally ments for a reliable exchange of pre- GWG developed so-called “PDF/X-Plus” press data; the ISO standard itself does specifications based on PDF/X-1a for not specify quality requirements. These more than a dozen market segments. requirements are different for each These segments were reduced to seven printing process (sheetfed offset, web in the latest GWG2015 specification for offset, newspaper printing, flexo print- heatset and coldset printing: ing, screen printing, etc.) and market segments (magazines, newspaper, art ■■Magazine Ads books, etc.). ■■Newspaper Ads For example, PDF/X does not de- ■■Sheetfed CMYK fine a minimum resolution for imag- ■■Sheetfed Spot es. It simply requires that images are ■■Web CMYK embedded (since external references ■■Web Spot are not allowed). There’s no reason ■■Web CMYK News why an image of 50 ppi can’t comply with the PDF/X specification because The following quality requirements the required minimum resolution de- (among others) are defined by the Ghent pends on the screen ruling as well as Workgroup for each market segment: the screening technology (AM or FM screening), and varies with the print ■■small text In 2005, the PDFX-ready associ- technology (ranging from newspaper ■■effective line width ation (www.pdfx-ready.ch) print to printing on coated stock with ■■use of spot colors was founded in Switzerland. high quality FM screening). ■■total ink coverage The main goal is to promote the The ISO committee responsible for ■■image resolution for grayscale and use of PDF/X standards by PDF/X made an early decision not to color images ­creators and receivers of attempt to include quality require- ■■image resolution for 1-bit images ­prepress data. ments for every PDF/X use case, but to ■■overprinting leave this task to organizations outside ■■PDF/X output intent the ISO. Among other benefits, this approach makes quality requirements The GWG2015 specifications are based easier to update than if they were part on PDF/X-4:2010, and for each market of the official ISO standard (which re- segment there are two variants: quires approximately three years for a change). ■■CMYK (and spot colors) only, and ■■CMYK+RGB which also allows ICC- Ghent (PDF) Workgroup based RGB images. The Ghent (PDF) Workgroup (www.gwg.org) took over the task of ICC-based colors for vectors and defining quality requirements. Known text are not allowed in GWG2015 informally as the “GWG”, the Ghent since they require the use of special Workgroup, founded in 2002, is an in- color management technologies at the ternational organization made up of print shop (e.g., to get pure black text) ­graphic arts users, associations & devel- which makes the files unpredictable. In opers building best practices for publish- addition, the use of ICC-based trans-

14 PDF/APDF/X in a in Nutshell a Nutshell 2.0 PDF/X-Plus parency blend modes is problematic in and preflight profiles for reliable PDF/X PDF/X-4 since the Adobe PDF Specifi- workflows. The deliverables are freely cation 1.6 on which PDF/X-4 is based available in German, French and (par- doesn’t clearly specify how to process tially) in English at www.pdfx-ready.ch. such objects. Since the goals of PDFX-ready are The Ghent Workgroup has started very similar to those of the Ghent working on an enhanced version al- Workgroup, PDF/X-ready joined the lowing more color spaces and more Ghent Workgroup and is a very ac- color managed objects using PDF/X-6 tive member. The preflight profiles of (based on PDF 2.0) which will clearly PDFX-ready are based on the GWG define processing of transparency with specifications but provide additional color management. checks and information. In addition to the GWG2015 spec- In addition, PDFX-ready offers a ification for commercial printing, family of certifications for its members: the Ghent Workgroup has also re- leased GWG2015 specifications for ■■Creator certification packaging. These are also based on ■■Output certification PDF/X-4:2010 and cover the following ■■Expert certification variants: PDFX-ready also publishes the pop- ■■Packaging Offset ular PDFX-ready Guideline (over ■■Packaging Gravure 250,000 downloads), which is updated ■■Packaging Flexo every year (available in German and English). PDFX-ready in Switzerland The latest developments are the In 2005, the PDFX-ready association PDFX-ready Online Tools which al- (www.pdfx-ready.ch) was founded in low anyone to upload PDF files to a Switzerland. The main goal of this or- cloud server for PDF preflight using the ganization is to promote the use of PDFX-ready profiles, color preflight and PDF/X standards by creators and re- a conversion from older color profiles to ceivers of prepress data via easy in- newer versions (ISO Coated V2 to PSO structions (called recipes), color and Coated V3 and vice-versa) using a free export settings for layout applications, Connector for Mac and Windows.

PDF/APDF/X in a Nutshell 2.0 15 PDF/X and the other PDF standards PDF/X and the other by Dietrich von Seggern PDF standards

Specialized ISO standards based on PDF/A-3 (published in 2012) is iden- the Portable Document Format are tical to PDF/A-2 but allows for embed- available for a wide range of purposes. ding arbitrary file formats. It’s intended for controlled processes, and to provide PDF additional information to the PDF/A Originally developed by Adobe Sys- file such as formulas in a spreadsheet or PDF/X since 2001 tems in 1993, PDF 1.7 became an machine readable data in a XML file. “Prepress digital data open standard in 2008 as ISO 32000-1. ­exchange using PDF” PDF 2.0 will be published in 2017. PDF/E (ISO 24517) Printing industry Based on Adobe’s PDF 1.6, this stan- PDF/A (ISO 19005) dard has been available since 2008. It PDF/A is designed to provide a robust is aimed at engineering documents PDF/A since 2005 digital file format replacing traditional such as construction drawings and “PDF Archive” paper or digital TIFF archives. Design is usually derived from CAD files. Long-term archiving goals of PDF/A include consistency, PDF/E can display rotating and fold- completeness and an unambiguous ing 3D objects on-screen, using tools internal structure. The archival spec- like Adobe Reader. An update to PDF/E since 2008 ification for PDF is not only used in PDF/E based on PDF 2.0 is currently “PDF Engineering” archives, but also in cases where the under development. Construction diagrams reliability of digital documents is cru- with accurate measure- cial, e.g. in the exchange of construc- PDF/VT (ISO 16612-2) ments and live 3D models tion data between companies. PDF/VT, published in 2010, supports The standard’s first part, PDF/A-1, variable data printing as is often used was published in 2005. The technical for invoices or personalized advertise- PDF since 2008 concepts at work in this specification ments. “VT” stands for “variable data “Portable Document Format” are based on experience with PDF/X and transactional printing”. PDF/VT Corresponds with Adobe’s (fonts must be embedded, colors must requires conformance with PDF/X-4. PDF version 1.7 be defined in a device independent way, etc.). In turn, some of the more PDF/UA (ISO 14289) detailed provisions of PDF/A (e.g., The “UA” in PDF/UA, originally pub- PDF/VT since 2010 font encoding and metadata) were lished in 2012, stands for “Universal “PDF for Variable Data and adopted by PDF/X-4 in 2010. PDF/A Access”. This specification includes Transactional Printing” defines two conformance levels; PD- provisions for making PDF files ac- Variable data printing F/A-1b is the “basic” version while cessible to users with disabilities who additional requirements pertaining must use assistive technology (AT) to to searchability and accessibility, are read. In this context, so-called “Tagged PDF/UA since 2012 covered in PDF/A-1a. PDF” provides the necessary structur- PDF/A-2, published in 2011, differs al information to enable navigational “PDF for Universal Access“ from PDF/A-1 in that it is based on aids, reading software or Braille dis- Universally accessible ISO 32000-1 (see above). This change plays to navigate and present page con- PDF documents makes conversion to PDF 1.4 (as re- tent (text, images, diagrams, etc.). quired by PDF/A-1) unnecessary, so Correct structure information also en- users leveraging features of PDF 1.7 ables reuse of PDF content, for example need not lose those features when to reflow a document’s text on a mobile making PDF/A files. device to improve the reading experience.

16 PDF/APDF/X in a in Nutshell a Nutshell 2.0 PDF/X in a Nutshell PDF for printing – The ISO standard

PDF/X was the first ISO standard based on About the PDF Association PDF technology. A subset of the PDF specification, The PDF Association promotes the adoption PDF/X was designed to constrain PDF files in order and implementation of international standards to cater to specific use-cases in the print industry. for PDF technology. Contents: The activities of the PDF Association include education and promotion of ISO 32000 (the ■ ■The history of PDF/X international standard for PDF), as well as PDF/A, PDF/E, PDF/UA, PDF/VT and PDF/X. We work ■■PDF/X: The key facts closely with ISO on the development of future ■■Technical side and requirements of PDF/X PDF standards. ■ The PDF Association includes members from over ■Users and industry segments 20 countries world-wide. ■■Tools and usage For more information go to www.pdfa.org

■■PDF/X-Plus

■■PDF/X and the other PDF standards