What is PDF/X and why is it important?

PDF/X is a subset of the Portable Document Format (PDF) specification that is specifically designed for print submission. It is not just a file format but also an application standard as it defines how applications creating and reading PDF/X files should behave.

PDF/X restricts the content in a PDF document that does not directly serve the purpose of high-quality print production output, such as annotations, Java Actions, and embedded multimedia. By optimizing the PDF just for print purposes there are likely to be fewer errors. To further reduce errors, a PDF/X file will have embedded fonts and graphics with all elements encoded as either CMYK or Spot. It is also designed to overcome various Overprint/trap issues.

How it works

The render intent identifies the press condition the file is prepared for, such as type of press and the inks and paper that will be used.
If you send PDF/X-1a compliant files, you should never again have to worry about being asked to supply missing fonts or images. You should never again have to be concerned about an image being converted from RGB to CMYK without seeing the results. Decisions about whether or not the printer should trap your file will be based on reliable information. And finally, the printer will know if the file was prepared properly for the press it is going to print on.

PDF/X Types
There are currently two main types of PDF/X; PDF/X-1a and PDF/X-3. Each PDF/X type contains its own set of restrictions as to what is or is not acceptable in a PDF. The PDF/X-3 standard is a superset of PDF/X-1a (a PDF/X-1a file meets all of the requirements of PDF/X-3), and all of the tools designed to read PDF/X-3 are also able to read PDF/X-1a files. A major distinction between the two is that a PDF/X 3 file can also contain colour-managed data.

Why We Selected PDF/X-1a
The Pass4Press Committee recognizes that the existing PDF/X-1a standard has significant value that will not decrease for a considerable time.  However, we have to also be able to try to implement this standard in the most universally acceptable way, to ensure mass adoption. For instance, while PDF/X-3 includes the benefit of colour management into the mix, this requires strong understanding of such matters by all involved. It was felt by the PPA that the UK industry was not quite at the implementation level required to make this widely successful.

Currently and for the foreseeable future the PDF/X-1a standard has the most momentum and acceptance. We will continually monitor emerging standards and implement them as soon as it makes sense for everyone concerned. PDF/X-1a is another important step in our goal to have files and work within the industry that reduce errors, cost and ultimately speeds up the process.

Future PDF/X Standards
Defining new PDF/X standards is a difficult balancing act of embracing the benefits of earlier standards while adding real value as part of a new standard.  In order to avoid confusion, the next PDF/X standards will not be a revision of PDF/X-1a and/or PDF/X-3 but will be known as PDF/X-4 and PDF/X-5 respectively. They will be a superset of PDF/X-3, in that they will allow the same kinds of usage of device independent color spaces. They also add the following features based on the current specifications:

• Transparency
• Layers
• Embedding OpenType fonts
• 16-bit images
• External links to fonts, ICC profiles and XObjects

The PDF/X-4 and PDF/X-5 standards specifications are likely to be published and approved in 2007.

Top 10 Problems with PDF files

Unfortunately things can go wrong with a PDF file, even with the best intentions. Here are the top 10 features of problematic PDF’s. Try to ensure they don’t occur with yours.

1.  Image resolution too low
2.  Fonts not embedded
3.  Wrong colour space
4.  Incorrect trim or bleed information
5.  Inconsistency with native file (hairlines, gradients)
6.  Spot color misnamed or converted to process
7.  Too much compression (artifacts, quality loss)
8.  Incorrect page size information
9.  Transparent object issues
10. Incorrect or missing ICC profile

Based on Seybold PDF Usage Survey of over 2000 PDF creators and receivers, Autumn 2004