20 years of PDF/X: From PDF/X-1a to PDF/X-6
Today’s PDF/X-6 standard was developed to support increasingly complex PDF print publishing workflows, from content creation to rendering and finishing.
The first ISO PDF/X standard is now over 20 years old. In this second part, we look at the various PDF/X sub-formats that were developed over the years. You can find the first part of our PDF/X article series here.
Further developments based on PDF/X-1a
Since 2001, new PDF/X versions have gradually been developed. After PDF/X-1a, PDF/X-4:2008 (ISO 15930-7:2008) and its update PDF/X-4:2010 (ISO 15930-7:2010) deserve special mention. This is currently the most suitable PDF/X variant for content with transparency effects.
What are the advantages and special features of the individual versions?
In 20 years, several variants have been developed with different adaptations. The standards are identified by a year and for each variant there is an individual version of the ISO standard.
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The first standard was ISO 15930-1: PDF/X-1a:2001. This format is limited to CMYK and spot colors, based on PDF 1.3.
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ISO 15930-3: PDF/X-3:2002 is an extension based on PDF 1.3. It allows color-calibrated data exchange in color spaces beyond CMYK and spot colors, such as RGB and Lab. It also adds ICC color management for objects inside the PDF file, not only for the output intent. This PDF/X version supports full blind exchange and is supported by major graphics applications and RIPs, but adoption remained limited in Europe and very low in other regions (especially North America).
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ISO 15930-4: PDF/X-1a:2003 updates the 2001 version of PDF/X-1a based on PDF 1.4. Most importantly, CMYK and spot colors in any combination are supported. PDF 1.4 added robust support for live object transparency (including transparency groups and blending modes). Adobe PDF 1.5 later added JPEG 2000 image compression, optional content groups, and object streams with compression.
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PDF/X-4: PDF/X-4:2008 (ISO 15930-7:2008) and its update PDF/X-4:2010 (ISO 15930-7:2010) are based on PDF 1.6 and include the color support of PDF/X-3 plus additional PDF 1.6 features, including limited layer support (optional content groups), compressed object streams, and some JPEG 2000 support. It is currently the most suitable PDF/X format for content with transparency effects.
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PDF/X-5: PDF/X-5 (i.e., PDF/X-5:2008 (ISO 15930-8:2008) and PDF/X-5:2010 (ISO 15930-8:2010)) was developed based on Adobe PDF 1.6 as a special version of PDF/X-4. At this time, no major graphics applications are known to support any PDF/X-5 conformance levels.
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PDF/X-6: With PDF/X-6:2020 (ISO 15930-9:2020), PDF/X-4 was extended by various PDF 2.0 functions. The PDF/X-6 conformance level enables full blind exchange.
More info: https://www.pdfa.org/twenty-years-of-pdf-x-part-iii/
What about PDF/X-2?
It is noticeable that a PDF/X-2 standard is rarely mentioned. This is because PDF/X-2:2003 (ISO 15930-5:2003) was withdrawn not long after publication. There are no known applications that support PDF/X-2.
Since 2020: With PDF 2.0, there was also a new standard for PDF/X: PDF/X-6
Based on ISO 32000-2:2020 (PDF 2.0), PDF/X-6:2020 (ISO 15930-9:2020) extends the graphics support of PDF/X-4 to include a wide range of PDF 2.0 features, including support for black point compensation, output intents per page (with optional CxF/X-4 spectral data), and document part metadata. The use of annotations within the visible page area, as well as non-XFA forms, digital signatures, and some actions, is now allowed with notable restrictions.
The PDF/X-6 conformance level allows full blind exchange. Carefully created PDF/X-6 files with some restrictions can be simultaneously marked as conforming PDF/A-4 files for archiving. The PDF/X-6 and PDF/A-4 standards were developed at the same time and care was taken in the development of the standards to ensure this commonality.
As of now, there are no known major graphics applications that support any of the PDF/X-6 conformance levels. It may still take time before broad PDF/X-6 creation support is available in major graphics applications. Until then, it is recommended to continue using the PDF/X-4 standard.
Today's print jobs and requirements
Today's print jobs are increasingly packaging, signage (including large posters and vehicle wraps), artwork, textiles, wall coverings, personalised marketing campaigns, etc. The content of today's print jobs is typically much more complex than the content of 20 years ago. Thanks to digital photography and more powerful design tools, colour and sophisticated transparency effects are becoming increasingly important for print. This includes colours outside the typical CMYK colour gamut.
Increasingly, the concept of a 'print job' goes far beyond one or more pages in one format printed on just one substrate (or paper type) on one press. For example, a book may contain a cover, monochrome text pages on matte paper, fold-in pages and colour pages on thicker, glossy paper. A similar example is variable data printing, where multiple pages, cards, envelopes, etc. are produced as part of a personalised mailer. These different page types may require pages to be 'pulled' from different trays or even printed in parallel on multiple devices to be joined together afterwards.
Printers no longer have the luxury of adapting a PDF file so that the content only renders correctly on a single type of device in a particular location. And these devices are much less likely to be CtP (computer-to-plate) devices that support offset printing; digital printing is an increasingly large target for print jobs, especially short-run and/or variable-data jobs. If only for operational purposes, ICC colour management is no longer optional or a feature. Certain functions should be supported as a matter of urgency, including ICC colour management and some functions such as annotations under certain conditions (such as comments, marks, forms, etc.). Thus, the PDF/X standards have also been revised and adapted again and again.
More on the adaptations of the individual sub-formats can be found in the detailed article series at pdfa.org: