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About the contributor
Dietrich von Seggern

After receiving his degree as printing engineer, Dietrich von Seggeern is in 1991 starting his professional career in the area of processing of digital print data. He is involved in several research projects around data transmission in publishing using at that time new broadband networks. In this context he is also working on standardization of digital data formats and in 1997 he encounters for the first time the PDF format for these purposes. Since 2002 he is working for callas software in several leading professions. One of his main focusses is the international standard for PDF in digital archives: PDF/A. callas software was involved in the standardization process at ISO before the first part is published in 2005; further standard parts, PDF/A-2 and PDF/A-3 follow.
More contributions
Participating in the PDF Techniques Accessibility Summit

The PDF Techniques Accessibility Summit’s objective is to establish a broad-based understanding of how PDF files should be tagged for accessibilty. It’s an opportunity to focus on establishing a common set of examples of accessible PDF content, and identify best-practice when tagging difficult cases.

Modernizing PDF Techniques for Accessibility

The PDF Techniques Accessibility Summit will identify best-practices in tagging various cases in PDF documents. Questions to be addressed will likely include: the legal ways to tag a nested list, the correct way to caption multiple images, the appropriate way to organize content within headings.

Refried PDF

My hospital emailed me a medical records release form as a PDF. They told me to print it, fill it, sign it, scan it and return it to the medical records department, in that order. In 2018? To get the form via email (i.e., electronically), yet be asked to print it? Did the last 20 years just… not mean anything! So I thought I’d be clever. I’d fill it first, THEN print it. Or better yet, never print it, but sign it anyhow, and return it along with a note making the case for improving their workflow. The story continues…

Slides and video recordings of PDF Days Europe 2018

You missed the PDF Days Europe 2018? Never mind! Here you can find the slides and video recordings of all 32 stunning sessions!

Using PDF/UA in accessibility checklists

PDF/UA, like PDF itself, is internally complex, but used correctly, actually makes things easier.

PDF/X and the other PDF standards

by Dietrich von Seggern

Specialized ISO standards based on the Portable Document Format are available for a wide range of purposes.


Originally developed by Adobe Systems in 1993, PDF 1.7 became an open standard in 2008 as ISO 32000-1. PDF 2.0 will be published in 2017.

PDF/A (ISO 19005)

PDF/A is designed to provide a robust digital file format replacing traditional paper or digital TIFF archives. Design goals of PDF/A include consistency, completeness and an unambiguous internal structure. The archival specification for PDF is not only used in archives, but also in cases where the reliability of digital documents is crucial, e.g. in the exchange of construction data between companies.

The standard’s first part, PDF/A-1, was published in 2005. The technical concepts at work in this specification are based on experience with PDF/X (fonts must be embedded, colors must be defined in a device independent way, etc.). In turn, some of the more detailed provisions of PDF/A (e.g., font encoding and metadata) were adopted by PDF/X-4 in 2010. PDF/A defines two conformance levels; PDF/A-1b is the “basic” version while additional requirements pertaining to searchability and accessibility, are covered in PDF/A-1a.

PDF/A-2, published in 2011, differs from PDF/A-1 in that it is based on ISO 32000-1 (see above). This change makes conversion to PDF 1.4 (as required by PDF/A-1) unnecessary, so users leveraging features of PDF 1.7 need not lose those features when making PDF/A files.

PDF/A-3 (published in 2012) is identical to PDF/A-2 but allows for embedding arbitrary file formats. It’s intended for controlled processes, and to provide additional information to the PDF/A file such as formulas in a spreadsheet or machine readable data in a XML file.

PDF/E (ISO 24517)

Based on Adobe’s PDF 1.6, this standard has been available since 2008. It is aimed at engineering documents such as construction drawings and is usually derived from CAD files. PDF/E can display rotating and folding 3D objects on-screen, using tools like Adobe Reader. An update to PDF/E based on PDF 2.0 is currently under development.

PDF/VT (ISO 16612-2)

PDF/VT, published in 2010, supports variable data printing as is often used for invoices or personalized advertisements. “VT” stands for “variable data and transactional printing”. PDF/VT requires conformance with PDF/X-4.

PDF/UA (ISO 14289)

The “UA” in PDF/UA, originally published in 2012, stands for “Universal Access”. This specification includes provisions for making PDF files accessible to users with disabilities who must use assistive technology (AT) to read. In this context, so-called “Tagged PDF” provides the necessary structur.al information to enable navigational aids, reading software or Braille displays to navigate and present page content (text, images, diagrams, etc.).

Correct structure information also enables reuse of PDF content, for example to reflow a document’s text on a mobile device to improve the reading experience.


PDF Standard Introduced Purpose Segment
PDF/X  since 2001 “Prepress digital data exchange using PDF” Printing industry
PDF/A  since 2005 “PDF Archive” Long-term archiving
PDF/E  since 2008 “PDF Engineering” Construction diagrams with accurate measurements and live 3D models
PDF  since 2008 “Portable Document Format” Corresponds with Adobe’s PDF version 1.7
PDF/VT  since 2010 “PDF for Variable Data and Transactional Printing” Variable data printing
PDF/UA  since 2012 “PDF for Universal Access” Universally accessible PDF documents

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Tags: PDF/X in a Nutshell
Categories: PDF, PDF 2.0, PDF/X