The PDF/VT file format

PDF/VT is a special flavor of the PDF file format that is specifically geared towards variable data printing (VDP) in a variety of environments, from desktop printing to digital production presses.
The V and T in PDF/VT actually stand for Variable and Transactional. Variable data printing refers to any printing in which part of the content is different for each recipient. It is used a lot in direct mail. Transactional printing includes invoices, statements and transpromo (documents that combine billing information with marketing information).

The PDF/VT standard was published in the fall of 2010 as an official ISO standard: ISO 16612-2.

This page contains the following sections:

  • What is a PDF/VT file?
  • Which types of PDF/VT files exist?
  • How to create PDF/VT files
  • How to view PDF/VT files
  • How to process PDF/VT files
  • Competing standards
  • Other sources of information

What is a PDF/VT file?

A PDF/VT file is a PDF file. It has the same icon and .pdf file extension as any other PDF file.

PDF/VT is however a very special flavor of PDF. It is first of all based on two existing standards for print job exchange: PDF/X-4 (ISO 15930-7) and PDF/X-5 (ISO 15930-8). This means that:

  • PDF/VT files are regular PDF 1.6 files.
  • The use of transparency is allowed.
  • All color data can be grayscale, CMYK, named spot colors, RGB, Lab or ICC-profile based.
  • Image data can be 8-bit or 16-bit. 16-bit images are still rarely used and may cause issues with quite a few RIPs or workflows.
  • The use of layers is allowed. In PDF/X-4 and PDF/X-5 these are not the ‘regular’ PDF layers (OCG or Optional Content Groups for the techies among us) but the more sophisticated OCCD layers (which actually combine multiple OCGs in a group). If a regular PDF has for instance a layer with comments and another one with contact information, both layers could be combined in a single ‘info’ OCCD layer.

The following restrictions apply to PDF/X-4 and PDF/X-5 files, and as such to PDF/VT files as well:

  • All fonts must be embedded in the file. Embedding OpenType fonts is allowed.
  • OPI is not allowed in PDF/X-4 files: all image data must be embedded.
  • Compliant files cannot contain music, movies or non-printable annotations.
  • If there are annotations (sticky notes) in the PDF, they should be located outside the bleed area.
  • The file should not contain forms or Javascript code.
  • Only a limited number of compression algorithms are supported, JPEG 2000 being one of them.
  • Encryption cannot be used.
  • Transfer curves cannot be used.

Next to things that are not allowed, there is also some information that must be present in a PDF/X file but that you may not find in regular PDF files:

  • There is an extra line of information which indicates that the PDF file is a PDF/X-4 or PDF/X-5 file.
  • There is a separate flag (meaning a switch that is either ON or OFF) that details whether the file has already been trapped or not.
  • PDF/X files contain extra operators that define the bleed and trim area.
    • The MediaBox defines the size of the entire document
    • The ArtBox or TrimBox defines the extent of the printable area.
    • If the file is to be printed with bleed, a BleedBox must be defined. It must be larger than the TrimBox/ArtBox, but smaller than the MediaBox.
  • The file needs to contain an output intent which describes the intended printing condition. The output intent is either:
    • an ICC color profile. Profiles can be embedded or referenced (in such a case when ICC profiles are externally supplied, such a file is called a PDF/X-4p file).
    • an output condition identifier, which is simply a text description of the intended print specifications (e.g. FOGRA27).

Which types of PDF/VT files exist?

There are 3 different flavors of PDF/VT:

  • PDF/VT-1 – With PDF/VT-1 all the layout data and variable data are embedded in one single file. This is the most straightforward: there is one single PDF file and it contains all of the data you need for output.
  • PDF/VT-2 – With PDF/VT-2 the main PDF file can reference to additional external PDF objects. One of the advantages of linking to additional files is that it becomes easier to create very large datasets.
  • PDF/VT-2s – With PDF/VT-2 live streaming is supported. This allows segmented sections of data to be processed.

How to create a PDF/VT file

A number of vendors such as HP and XMPie are currently creating tools to generate PDF/VT files. Many of the products will be for web-to-print products.

How to view a PDF/VT file

PDF/VT sample files can be found at the PDFlib site.

A PDF/VT-1 files can be viewed in Adobe Viewer and Adobe Acrobat. I haven’t tried any other viewers yet.

The individual PDF files of a PDF/VT-2 set can also each be viewed in any PDF viewer. I haven’t found any tool yet that can display merged results onscreen.

How to process a PDF/VT file

Adobe is one of the driving forces behind the PDF/VT standard. The 2.5 version of their Adobe PDF Print Engine (APPE) software can be used to process PDF/VT files. You cannot buy APPE directly since this software is sold to vendors like Agfa, Kodak and Fujifilm who incorporate this engine in their workflow products. Consult with your workflow vendor if the workflow you use is already capable of processing PDF/VT files.

Kodak, Fujifilm, HP and EFI are known to be working on PDF/VT support in (some of) their products.

Competing standards

PDF/VT is a fairly late entry in the world of variable data processing. There are many other standards on the market, which are more established and more widely used. The most important one is PPML (Personalized Print Markup Language), an XML-based print language for personalized print that was first introduced in 2000 and is now in its 4th generation.

Other sources of information

PDFlib has a page dedicated to the PDF/VT file format. It includes an interesting white paper.

9 August 2013

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