by Andrew Bailes-Collins
Where do all these different flavors of PDF/X fit, and for anybody wanting to use PDF/X, which versions should they investigate?
For those considering moving to a PDF/X-based workflow it’s critical that the chosen PDF/X version fits the capabilities and objectives of that workflow. If the workflow and output RIP are relatively modern (purchased within the last 3-4 years), it will almost certainly be able to work with the latest PDF functionality such as live transparency and layers. In this situation, PDF/X-4 is highly recommended.
In an older workflow system that has difficulty digesting some of the newer PDF functionality such as transparency, it’s probably not a good idea to attempt adopting PDF/X-4; an older PDF/X version is probably more suitable.
It’s important to leverage the free dedicated test suites that allow users to evaluate their workflow for PDF/X-4 readiness; the Ghent PDF Workgroup (GWG) Output Suite is one such.
When testing, all applications within a workflow must be considered, including (but not limited to): imposition software, color servers, ink saving software, trapping software, and output RIPs.
The benefit for a design company in working with PDF/X is that it’s easier than coping with a myriad of PDF creation settings from different printing companies and suppliers.
The output settings needed to create valid PDF/X files are pre-configured into most professional page layout and design applications, so generating a PDF/X file is just a matter of selecting the required PDF/X version, and ensuring the file is compliant after creation.
If an artwork creator supplies a conforming PDF/X file, then any print service provider should have the tools and knowledge to be able to process and print that file without problems, the key rationale and value proposition that underpins the PDF/X standards.
Magazines and newspapers often integrate content produced elsewhere (e.g., advertising) into their products. Typically, these publishers produce very detailed specifications on how a PDF file should be created and checked before they receive it. Due to the sheer volume of content they receive and deliver, and the deadlines they work to, they normally expect any incoming advertising files to be correct when delivered.
The production for these types of publications is split into two distinct areas, receiving files for advertising, and delivering final pages for print.
Since smooth workflows is of critical interest to these businesses, magazines and newspapers were among the very early adopters of PDF/X. New York’s Time Inc. is credited with the first known use of a PDF/X-1 file in live production, when they ran an advertisement for Bayer in the March 13, 2000 issue of TIME magazine.
Today, most newspapers and magazine publishers have joined Time, Inc. in adopting PDF/X. Most of these businesses require all advertising to be delivered as a PDF/X-1a file, and in turn deliver their final pages to the printer as PDF/X-1a files.
It’s fair to ask: why haven’t periodical publishers embraced the newer versions of PDF/X, such as PDF/X-4? The answer is straightforward; their current workflows are working predictably and correctly. Another limitation is the fact that as yet, many suppliers and stakeholders in the production chain are currently unwilling to accept responsibility for flattening transparencies, and handling other PDF/X-4 functionality. Until recently, to these publishers, the risks in handling the latest versions of PDF/X has not been worth the benefits of making the transition, but this is now changing.
A key driver for this change is that PDF/X-1a files are not very useful when it comes to re-purposing content. However, newspaper and magazine publishers increasingly need to develop cross-media content that’s optimized for tablet or online publication. This requirement, along with the gradual acceptance of modern production techniques, is driving the newspaper and magazine publishing industry towards PDF/X-4.
Commercial and digital printers jumped on PDF/X-1a when it was released. For many of these companies, it is still the standard they use for the same reasons as the periodical publishers discussed earlier: predictability and responsibility.
When it was first released, live transparency caused a major problem for printing companies, as their output RIPs and workflows were not capable of handling it correctly. In many cas.es, their output devices were based on PostScript, so files with transparency needed to be flattened prior to output to ensure correct results and avoid waste and spoilage.
In today’s commercial and digital printing marketplace, however, PDF/X-4 is very much in use. If you have a modern workflow and output RIP, then you are more than capable of handling a PDF/X-4 file.
One aspect of PDF/X-4 that often causes concern, particularly in sheetfed and web offset, is the fact that color spaces such as RGB and Lab are allowed. Many printers are not confident in handling files that contain these color spac.es, and prefer to handle only CMYK and spot color based files. It is, however, perfectly possible to use PDF/X-4 based preflight configurations that forbid these color spaces (i.e., permitting only a subset of PDF/X-4). The newer GWG preflight specifications (see “Further quality requirements: PDF/X-Plus”) are all based on PDF/X-4.
In digital printing, particularly with output engines that have large color gamuts, RGB based files are beneficial, as they can use the full color gamut available in the press rather than constraining the color gamut to that of a conventional CMYK based process.
PDF/X-1a, PDF/X-3 and PDF/X-4 are all relevant to large format printing, but there are certain aspects of each that should be recognized. The choice of format will depend on the type of work, the workflow and knowledge of the printing company in question. These aspects are fundamentally the same as those discussed in the commercial print section above.
One attribute of a PDF file that can be a requirement for large format printing is the ‘user unit’. A PDF file (prior to PDF 2.0, which allows pages measurable in kilometers) has a technical size limitation of 200 x 200 inch.es, which is fine for most commercial printing, but when you want to print a poster that covers the side of a building, this limitation becomes an issue. To overcome this size limitation the PDF 1.6 specification included a function called ‘UserUnit’ which effectively enables the size of the PDF to be scaled by a multiplication factor, allowing the creation of larger page sizes.
The PDF/X-4 specification is based on PDF 1.6, so if it’s a requirement that PDF files are supplied at their correct size, then PDF/X-4 would be needed.
However very often in this market, files are supplied at a smaller size than the final required size, and are enlarged on output. This is a more traditional method of working, and has been the case since the days when film supplied as a reduced size version would be projected on a large camera to the correct final size.
Digital large format devices very often have large multi-color ink sets to deliver a wide color gamut. Some devices have up to 12 inks to maximize the quality of printing, and can produce most available spot colors (excepting special inks such as metallic).
The output RIPs on these devices often have very sophisticated color management functionality in order to work with these ink sets, and it makes sense that PDF files being printed should maximize this capability. In this case PDF/X-3 or PDF/X-4 can be useful as they allow color-managed color spaces such as Lab, CalRGB or use of an embedded ICC profile.
When investigating PDF/X for large format, a key consideration is the output RIP driving the printer. There are a large variety of different large format RIPs available, with different quality and functionality. Thorough testing is advisable to ensure the output of the required PDF/X level is correct and predictable, before implementing a PDF/X based workflow. The GWG output suite mentioned above usually proves to be very useful in such testing.
Label and packaging differs from other methods of print production for sever.al reasons. A key distinction is that the size of the final job is often not a square or a rectangle, so it cannot be defined by a PDF page box. Additionally, in packaging, the use of multiple spot color inks rather than just CMYK is very common, with spot colors frequently used in image separations as well as in text and vector graphics.
Additionally, within modern packaging production, extended gamut printing is becoming more prevalent, especially with digital devices. Extended gamut printing uses a fixed ink set of CMYK plus additional spot colors (orange, violet and green are typical) to produce a very large color gamut, allowing a large range of spot colors to be produced without the need to run individual spot color inks.
All PDF/X formats require that an output intent is defined (see “Technical side and requirements of PDF/X”) that uses an ICC profile to characterize the intended output. Output intents use normally CMYK ICC profiles, but for PDF/X-4 or PDF/X-3 that can also be RGB or even Gray profiles.
To fully support multi-channel workflows with PDF/X, a multi-channel color profile is required. Multi-channel profiles are not supported by any of the previously mentioned PDF/X standards. The only PDF/X version which that allows for multi-channel profile support is PDF/X-5n
As of this writing, PDF/X usage in the label and packaging market is not widespread, but with PDF 2.0 and the upcoming PDF/X-6, functionality will be added to make adoption easier and more beneficial.