Rules for Accessible PDF: Matterhorn Protocol 1.1 is now available

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The PDF Association's PDF/UA Technical Working Group is pleased to announce the immediate availability of version 1.1 of the Matterhorn Protocol.
An algorithm establishing failure criteria for accessible PDF documents, the Matterhorn Protocol promotes adoption of PDF/UA - the ISO standard for accessible PDF - by software developers, service bureaus, end users and others interested in validating PDF document accessibility.
Updated in 2021 this release adds a new failure condition and provides several clarifications; the Matterhorn Protocol 1.1 consists of 31 Checkpoints comprised of 136 Failure Conditions. The PDF file is tagged to reflect current best-practice in tagging PDF documents for accessibility and reuse.
NOTE: The Matterhorn Protocol 1.1 PDF conforms to both PDF/UA-1 (ISO 14289-1) and to PDF/A-2a (ISO 19005-2), and is presented as a reference-quality PDF/UA file.