Established over 13 yearsThe History of PAC

PACs success story is based on the commitment of many people and organizations who have contributed their time, knowledge or financially over the years to make PAC, a free PDF accessibility checking tool, aligned to global standards. We would like to thank them here and outline a few important milestones.

11-2023PAC 2024 released

PAC 2024 has a new, fresh design and logo. For the first time, PAC offers quality checks that are designed to save time and effort during manual testing.

11-2023PAC has its own Website

To make PAC available free of charge in the future and to ensure its further development and maintenance, axes4 is hosting PAC on its own website:

08-2021PAC 2021 released 

The PDF/UA Foundation is the new home of PAC. The 2021 release includes enhanced features like the WCAG check set.  

04-2021Matterhorn Protocol 1.1 

The 1.1 release of the Matterhorn Protocol adds a new failure condition and provides several clarifications.  

12-2017PAC 3 released 

The PAC 3.0 release is available with a German user interface and a printable Summary Report.  


Roberto Bianchetti, Markus Riesch and Andreas Uebelbacher present their scientific paper “PDF Accessibility Checker (PAC 2): The First Tool to Test PDF Documents for PDF/UA Compliance“ at the 14th International Conference on Computers Helping People with Special Needs (ICCHP) in Paris (France). 

07-2014PAC 2 released 

Again a world premiere: The release of PAC 2.0 is the first global tool to test PDF documents for PDF/UA compliance.  

08-2013Matterhorn Protocol 1.0 

The Matterhorn Protocol 1.0 is published by the PDF Association. It’s a list of all the possible ways to fail PDF/UA-1, and simplifies the support of the ISO standard for software developers and service providers. 


PDF/UA is published as an ISO standard (ISO 14289-1:2012). UA stands for Universal Accessibility. It defines all essential requirements for accessible PDF documents, PDF software, and assistive technology for creating, checking, and using PDF/UA compliant files. 

08-2012PAC 1.3 released 

The release of PAC 1.3 introduces a new detailed report. It simplifies locating the issues directly in the document view.  


Markus Erle and Samuel Hofer present their scientific paper “Validity and Semantics – Two Essential Parts of a Backbone for an Automated PDF/UA Compliance Check for PDF Documents“ at the 13th International Conference on Computers Helping People with Special Needs (ICCHP) in Linz (Austria)  

09-2011PAC is picked up worldwide 

PAC is picked up by more organizations and experts around the world. For example, the German UPA (Usability Professionals Association) starts referencing it in their Digital Accessibility Guide. 

03-2010 PAC 1 Beta released 

A world premiere: PAC, the first free PDF accessibility checking tool, becomes available. It contains Syntax Checks and the very useful Screen Reader Preview.