The Matterhorn Protocol 1.0

Stylized image of the Matterhorn mountainWherever there’s economic activity, PDF files are the medium of recording for assessments and agreements, for conveying ideas and disseminating critical information. PDF files are, in many ways, red blood cells for the larger economy.

As the Matterhorn Protocol puts it: “The value of PDF may be stated in terms of the capacity to deliver a stable and trustworthy representation of a document.” Organizations worldwide rely on PDF for precisely this reason.

Unfortunately, many users experience PDF files as anything but trustworthy because they cannot effectively read them due to vision, mobility or other impairments.

In order for a PDF to be accessible to users who rely on special software features or devices (so-called “Assistive Technology”) to read, that PDF’s content must be “tagged.”

While tagged PDF became available in 2001, most PDF files created in 2013 still aren’t tagged. Even when they are tagged, today’s files usually offer disabled users a poor experience because the quality of the tagging is low.

The result for end users who depend on specialized technology to read is frustration and alienation. This is especially problematic for PDF because the format is so commonly used for bank statements, utility bills, mortgages, employment agreements and many other critical documents, not to mention everyday business correspondence. Today, most of these files are difficult or impossible for users who need technical assistance to navigate, read and interact with electronic documents.


Published in 2012, PDF/UA is the ISO Standard for accessible PDF files, software and assistive technology. It sets precise technical standards for accessible PDF files and establishes a high bar for quality in tagging.

But what is PDF/UA, really? It’s not software; it’s simply a document that describes the correct use of another document (ISO 32000) to achieve a certain outcome (ensure accessible PDF files).

To further assist software developers in coming to grips with PDF/UA, in 2012 the PDF Association began to develop a series of operational tests reflecting PDF/UA’s requirements, and thus allowing software to more easily share test results.

The Matterhorn Protocol

On August 7, 2013 the PDF Association announced the release of the Matterhorn Protocol 1.0.

To promote adoption of PDF/UA by software developers and document testers alike, the PDF Association’s PDF/UA Competence Center spent 15 months crafting the Matterhorn Protocol; a single table listing all the possible ways to fail PDF/UA. The document consists of 31 Checkpoints comprised of 136 Failure Conditions.

Each Failure Condition identifies a non-conforming condition for each of the hard requirements (so-called “shall statements”) in PDF/UA. Failure Conditions may apply to documents, pages, objects and JavaScripts. 89 of these Conditions may be assessed by machine alone; the rest require some level of human validation.

NOTE: A minor editorial update was posted in December 2013 with a date of October 10, 2013.

Going Forwards

The PDF Association’s PDF/UA Competence Center is proceeding with development of an XML-based formalization of the Matterhorn Protocol in order to provide software developers with a standardized parseable structure facilitating the sharing of validation results between applications.

Note for PDF Association Members: Any PDF Association member organization or individual is welcome to join the PDF/UA Competence Center’s listserv and meetings.

Implementations of Matterhorn Protocol 1.0

The developers of the following products were among the first to claim full support for the Matterhorn Protocol:

Download the Matterhorn Protocol.

About PDF Association

Founded in 2006 as the PDF/A Competence Center, the PDF Association exists to promote the adoption and implementation of International Standards for PDF technology.

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