At the beginning of 2020, in what we thought was the run-up to drupa, Global Graphics published a new guide called “Full Speed Ahead: How to make variable data PDF files that won’t slow your digital press”. It was designed to complement the recommendations available for how to maximize sales from direct mail campaigns, with technical recommendations as to how you can make sure that you don’t make a PDF file for a variable data job that will bring a digital press to its knees. It also carried those lessons into additional print sectors that are rapidly adopting variable data, such as labels, packaging, product decoration and industrial print, with hints around using variable data in unusual ways for premium jobs at premium margins.
Well, as they say, a lot has happened since then.
And some of that has been positive. At the end of 2020 several new International Standards were published, including a “dated revision” (a 2nd edition) of the PDF 2.0 standard, a new standard for submission of PDF files for production printing: PDF/X-6, and a new standard for submission of variable data PDF files for printing: PDF/VT-3.
We’ve therefore updated Full Speed Ahead to cover the new standards. And at the same time we’ve taken the opportunity to extend and clarify some of the rest of the text in response to feedback on the first edition.
So now you can keep up to date, just by downloading the new edition!
Last week was the first PDF 2.0 interop event in Cambridge, UK, hosted by Global Graphics on behalf of the PDF Association. The interop was an opportunity for developers from various companies working on their support for PDF 2.0 to get together and share sample files, and to process them in their own solutions. If a sample file from one vendor isn’t read correctly by a product from another vendor the developers can then figure out why, and fix either the creation tool or the consumer, or even both, depending on the exact reason for that failure.
When we make our own PDF sample files to test the Harlequin RIP there’s always a risk that the developer making the file and the developer writing the code to consume it will make the same assumptions or misread the specification in the same way. That makes testing files created by another vendor invaluable, because it validates all of those assumptions and possible misinterpretations as well.
It’s pretty early in the PDF 2.0 process (the standard itself will probably be published later this month), which means that some vendors are not yet far enough through their own development cycles to get involved yet. But that actually makes this kind of event even more valuable for those who participate because there are no currently shipping products out there that we could just buy and make sample files with. And the last thing that any of us want to do as vendors is to find out about incompatibilities after our products are shipped and in our customers’ hands.
I can tell you that our testing and discussions at the interop in Cambridge were extremely useful in finding a few issues that our internal testing had not identified. We’re busy correcting those, and will be taking updated software to the next interop, in Boston, MA on June 12th and 13th.
If you’re a Harlequin OEM or member of the Harlequin Partner Network you can also get access to our PDF 2.0 preview code to test against your own or other partners’ products; just drop me a line. If you’re using Harlequin in production I’m afraid you’ll have to wait until we release our next major version!
If you’re a software vendor with products that consume or create PDF and you’re already working on your PDF 2.0 support I’d heartily recommend registering for the June interop. I don’t know of any more efficient way to identify defects in your implementation so you can fix them before your customers even see them. Visit https://www.pdfa.org/event/pdf-interoperability-workshop-north-america/ to get started.
And if you’re a PDF software vendor and you’re not working on PDF 2.0 yet … time to start your planning!
About the author
Martin Bailey, consultant at Global Graphics Software, is a former CTO of the company and currently the primary UK expert to the ISO committees maintaining and developing PDF and PDF/VT. He is the author of Full Speed Ahead: how to make variable data PDF files that won’t slow your digital press, a guide offering advice to anyone with a stake in variable data printing including graphic designers, print buyers, composition developers and users.
To be the first to receive our blog posts,
To be the first to receive our blog posts, news updates and product news why not subscribe to our monthly newsletter? Subscribe here
In the middle of 2017 ISO 32000-2 will be published, defining PDF 2.0. It’s eight years since there’s been a revision to the standard. We’ve already covered the main changes affecting print in previous blog posts and here Martin Bailey, the primary UK expert to the ISO committee developing PDF 2.0, gives a roundup of a few other changes to expect.
Security
The encryption algorithms included in previous versions of PDF have fallen behind current best practices in security, so PDF adds AES-256-bit and states that all passwords used for AES-256 encryption must be encoded in Unicode.
A PDF 1.7 reader will almost certainly error and refuse to process any PDF files using the new AES-256 encryption.
Note that Adobe’s ExtensionLevel 3 to ISO 32000-1 defines a different AES-256 encryption algorithm, as used in Acrobat 9 (R=5). That implementation is now regarded as dangerously insecure and Adobe has deprecated it completely, to the extent that use of it is forbidden in PDF 2.0. Deprecation and what this means in PDF!
PDF 2.0 has deprecated a number of implementation details and features that were defined in previous versions. In this context ‘deprecation’ means that tools writing PDF 2.0 are recommended not to include those features in a file; and that tools reading PDF 2.0 files are recommended to ignore those features if they find them.
Global Graphics has taken the deliberate decision not to ignore relevant deprecated items in PDF files that are submitted and happen to be identified as PDF 2.0. This is because it is quite likely that some files will be created using an older version of PDF and using those features. If those files are then pre-processed in some way before submitting to Harlequin (e.g. to impose or trap the files) the pre-processor may well tag them as now being PDF 2.0. It would not be appropriate in such cases to ignore anything in the PDF file simply because it is now tagged as PDF 2.0.
We expect most other PDF readers to take the same course, at least for the next few years. And the rest… PDF 2.0 header: It’s only a small thing, but a PDF reader must be prepared to encounter a value of 2.0 in the file header and as the value of the Version key in the Catalog.
PDF 1.7 readers will probably vary significantly in their handling of files marked as PDF 2.0. Some may error, others may warn that a future version of that product is required, while others may simply ignore the version completely.
Harlequin 11 reports “PDF Warning: Unexpected PDF version – 2.0” and then continues to process the job. Obviously that warning will disappear when we ship a new version that fully supports PDF 2.0. UFT-8 text strings: Previous versions of PDF allowed certain strings in the file to be encoded in PDFDocEncoding or in 16-bit Unicode. PDF 2.0 adds support for UTF-8. Many PDF 1.7 readers may not recognise the UTF-8 string as UTF-8 and will therefore treat it as using PDFDocEncoding, resulting in those strings being treated as what looks like a random sequence of mainly accented characters. Print scaling: PDF 1.6 added a viewer preferences key that allowed a PDF file to specify the preferred scaling for use when printing it. This was primarily in support of engineering drawings. PDF 2.0 adds the ability to say that the nominated scaling should be enforced. Document parts: The PDF/VT standard defines a structure of Document parts (common called DPart) that can be used to associate hierarchical metadata with ranges of pages within the document. In PDF/VT the purpose is to enable embedding of data to guide the application of different processing to each page range.
PDF 2.0 has added the Document parts structure into baseline PDF, although no associated semantics or required processing for that data have been defined.
It is anticipated that the new ISO standard on workflow control (ISO 21812, expected to be published around the end of 2017) will make use of the DPart structure, as will the next version of PDF/VT. The specification in PDF 2.0 is largely meaningless until such time as products are written to work with those new standards.
The background
The last few years have been pretty stable for PDF; PDF 1.7 was published in 2006, and the first ISO PDF standard (ISO 32000-1), published in 2008, was very similar to PDF 1.7. In the same way, PDF/X‑4 and PDF/X‑5, the most recent PDF/X standards, were both published in 2010, six years ago.
In the middle of 2017 ISO 32000-2 will be published, defining PDF 2.0. Much of the new work in this version is related to tagging for content re-use and accessibility, but there are also several areas that affect print production. Among them are some changes to the rendering of PDF transparency, ways to include additional data about spot colors and about how color management should be applied.
In the middle of 2017 ISO 32000-2 will be published, defining PDF 2.0. It’s eight years since there’s been a revision to the standard. In his next blog post about the changes afoot, Martin Bailey, the primary UK expert to the ISO committee developing PDF 2.0, looks at halftones, an area where the new specification will offer significant benefits for flexo jobs.
Lists of spot functions in halftones PDF allows a PDF file to specify the halftone to be used for screening output in a variety of ways. The simplest is to identify a spot function by name, but that method was constrained in versions of the PDF standard up to PDF 1.7 to use only names that were explicitly listed in the specification itself. This has been a significant limitation in print sectors where custom halftones are common, such as flexography, gravure … and pretty much everywhere apart from offset plate-making!
PDF 2.0 allows the PDF file to specify the halftone dot shape as a list of spot function names, and those names no longer need to be picked from the ones specified in the standard. The renderer should use the first named spot function in the list that it supports. This allows a single file to be created that can be used in a variety of RIPs that support different sets of proprietary halftones and to select the best one available in each RIP for that specific object.
This functionality is expected to be used mainly for high-quality flexo press work, where it’s a key part of the workflow to specify which halftone should be used for each graphical element.
A PDF 1.7 reader will probably either error or completely ignore the screening information embedded in the PDF if a file using the new list form is encountered. In the flexo space that could easily cause problems on-press, so take care that you’ve upgraded your RIPs before you start to try rendering PDF files using this new capability.
Halftone Origin (HTO) Very old versions of PDF (up to PDF 1.3) included a partial definition of an entry named HTP, which was intended to allow the location of the origin or phase of a halftone to be specified. That entry was unfortunately useless because it did not specify the coordinate system to apply and it was removed many years ago.
PDF 2.0 adds a new entry called HTO to achieve the same goal, but this time fully specified. The use case is anywhere where precise specification of the halftone phase is valuable. Examples include pre-imposed sheets for VLF plate-setters, where specifying the halftone phase for each imposed page can reduce the misalignment of halftones that can occur over very long distances, or setting the halftone phase of each of a set of step-and-repeat labels to ensure that the halftone dots are placed in exactly the same position relative to the design in each instance.
A PDF 1.7 reader will simply ignore the new key, so there’s no danger of new files causing problems in an older workflow. On the other hand, those older RIPs will render as they always have, which would be a missed opportunity for the target use cases.
Halftone selection in transparent areas Up to PDF 1.7 there has been a requirement to apply the “default halftone” in all areas where transparency compositing has been applied. This was problematic for those print technologies where different halftones must be used for different object types to achieve maximum quality, e.g. for flexo. Transparency is used in these jobs most commonly for drop shadows, so that’s where you’re most likely to have encountered problems.
PDF 2.0 effectively gives complete freedom to renderers to apply the supplied screening parameters in whatever way they see fit, but two example implementations are provided to encourage similarity between implementations. One of those matches the requirements from PDF 1.7, while the other applies the screen defined for the top-most graphical element in areas where transparency was applied. The second one means that the screening selected for the drop shadow will now be used, matching requirements for the flexo market.
The background The last few years have been pretty stable for PDF; PDF 1.7 was published in 2006, and the first ISO PDF standard (ISO 32000-1), published in 2008, was very similar to PDF 1.7. In the same way, PDF/X‑4 and PDF/X‑5, the most recent PDF/X standards, were both published in 2010, six years ago.
In the middle of 2017 ISO 32000-2 will be published, defining PDF 2.0. Much of the new work in this version is related to tagging for content re-use and accessibility, but there are also several areas that affect print production. Among them are some changes to the rendering of PDF transparency, ways to include additional data about spot colors and about how color management should be applied.
I’ve been in the ISO PDF committee meeting in Sydney, Australia for a couple of days this week to review the comments submitted to the most recent ballot on PDF 2.0. Over 100 comments were received, including some complex issues around digital signatures, structure tagging (especially lists), optional content, document parts and soft masks. In all cases the committee was able to reach a consensus on what should be done for PDF 2.0.
The plan is now for one more ballot, the responses to which will be reviewed in Q2 next year, with an expectation that final text for PDF 2.0 will be delivered to ISO for publication shortly thereafter.
So we’re still on track for publication next year.
All of which means that it’s past time that a couple of PDF’s unsung heroes were acknowledged. The project leaders for PDF 2.0 have invested very substantial amounts of time and mental energy updating text in response to comments and ballots over the last several years. When somebody like me requests a change it’s the project leaders who help to double-check that every last implication of that change is explored to ensure that we don’t have any inconsistency.
So a big thank you to Duff Johnson of the PDF Association and Peter Wyatt of CISRA (Canon)!
It’s also worth noting that one of the significant improvements in PDF 2.0 that probably won’t get highlighted elsewhere is that the text now is much more consistent. When you’re writing a detailed technical document 1000 pages long it’s inevitable that some disconnections between different sections will creep in. PDF 2.0 illustrates the value of a broad group of people from many countries and many industries reviewing text in the ISO process: we’ve managed to stamp on many of those cases in this new version.
