What Is the Difference Between PDF/UA-1 and PDF/UA-2?

PDF/UA-1 (ISO 14289-1) and PDF/UA-2 (ISO 14289-2) are both ISO standards that define requirements for universally accessible PDF documents, but they are built on different versions of the PDF specification and differ significantly in their handling of mathematical content, semantic structure, and embedded files. PDF/UA-1, published in 2012, is based on PDF 1.7 and remains the dominant standard in practice. PDF/UA-2, published in 2024, is based on PDF 2.0 and introduces capabilities that address long-standing gaps in document accessibility — most notably native MathML support and a more flexible namespace system for structure elements.

For higher education institutions working toward accessibility compliance, understanding both standards is essential for making informed decisions about document workflows, tooling, and long-term strategy.

PDF/UA-1: The Established Standard

PDF/UA-1 was first published in 2012 as ISO 14289-1. It builds on the PDF 1.7 specification (ISO 32000-1) and establishes baseline requirements for accessible PDF documents. These requirements include:

• Tagged structure: Every piece of content must be tagged with a standard structure element (headings, paragraphs, lists, tables, figures, and so on).
• Reading order: The logical reading order must be deterministic and correct.
• Alternative text: Non-text content such as images must carry alternative text or be marked as artifacts.
• Font and character mapping: All fonts must allow characters to be mapped to Unicode.
• Navigation aids: Bookmarks, language identification, and document metadata must be present.

PDF/UA-1 has been the reference point for accessible PDF production for over a decade. It is the standard that most assistive technology vendors support, and it is the basis for validation tools like the Matterhorn Protocol, which provides a comprehensive set of test conditions for checking PDF/UA conformance.

If you are new to structured PDF accessibility, our overview of what PDF/UA is and why it matters covers the fundamentals.

PDF/UA-2: What Changed

PDF/UA-2 was published in 2024 as ISO 14289-2. It is based on PDF 2.0 (ISO 32000-2), which itself introduced a number of structural improvements to the PDF format. The key differences fall into four areas.

1. Native MathML Support

This is arguably the most significant improvement for higher education. PDF/UA-1 had no native mechanism for representing mathematical content accessibly. Equations were typically flattened into images with alt text — a workaround that fails for complex notation and makes content unusable for students who rely on screen readers or refreshable Braille displays.

PDF/UA-2 allows MathML to be embedded directly within the document structure. This means a screen reader can navigate an equation symbol by symbol, and Braille displays can render mathematical notation accurately. For STEM departments producing lecture notes, exams, and research papers, this is a substantial improvement.

2. Namespaces for Structure Elements

PDF 1.7 defined a fixed set of standard structure tags. PDF 2.0 introduces a namespace system that allows documents to reference and use structure elements from different specifications. PDF/UA-2 leverages this to support a richer, more extensible tag vocabulary.

In practice, this means documents can carry more precise semantic information. For example, rather than overloading a generic tag for a specific purpose, a document can declare exactly which specification defines the tag it is using. This improves interoperability and makes validation more reliable.

3. Associated Files

PDF 2.0 introduced the concept of associated files — the ability to embed related files (such as source data, alternative formats, or supplementary materials) and formally link them to specific structure elements within the document. PDF/UA-2 defines accessibility requirements for these associations, ensuring that embedded content is discoverable and navigable by assistive technology.

This is particularly useful for documents that bundle datasets, source code, or alternative renderings alongside the primary content.

4. Pronunciation Hints

PDF/UA-2 provides improved mechanisms for pronunciation metadata, allowing document authors to specify how particular terms, abbreviations, or symbols should be spoken by text-to-speech engines. While PDF/UA-1 supported language tagging at the document and element level, PDF/UA-2 extends this with finer-grained control.

Which Standard Should You Target Now?

For most institutions, PDF/UA-1 remains the practical target today. The reasons are straightforward:

• Tool support: The major PDF authoring and remediation tools — Adobe Acrobat, axesPDF, CommonLook, and others — have mature support for PDF/UA-1. PDF/UA-2 tooling is emerging but not yet widespread.
• Validation: The Matterhorn Protocol test suite is well established for PDF/UA-1. An updated version for PDF/UA-2 is in development but has not yet reached the same level of adoption.
• Assistive technology: Screen readers and other assistive technologies have been tested extensively against PDF/UA-1 documents. PDF 2.0 support in readers like NVDA and JAWS is still maturing.
• Regulatory alignment: Current accessibility regulations, including the DOJ ADA Title II requirements and EN 301 549 in Europe, reference WCAG 2.1 and do not mandate PDF/UA-2 specifically. Conformance to PDF/UA-1 satisfies the PDF accessibility expectations of these frameworks.

The Migration Path

The good news is that PDF/UA-1 and PDF/UA-2 are not in conflict. A well-structured PDF/UA-1 document already does most of what PDF/UA-2 requires at the structural level. When your tools and workflows are ready to move to PDF 2.0, the transition will be incremental rather than disruptive.

Institutions that produce significant mathematical or scientific content should monitor PDF/UA-2 tool support closely. Once your authoring pipeline can generate compliant PDF 2.0 files with embedded MathML, the accessibility gains for STEM content will be immediate and meaningful.

For now, the priority should be ensuring that your existing documents meet PDF/UA-1 requirements — proper tagging, reading order, alternative text, and metadata. Documents that meet this baseline today will be well positioned for PDF/UA-2 adoption when the ecosystem catches up.

Getting Started

Whether your goal is PDF/UA-1 compliance today or preparing for PDF/UA-2 in the near future, the first step is understanding where your document library stands. Aelira's PDF accessibility scanning tools can analyze your documents against current standards, identify structural issues, and help your team remediate problems efficiently — so your content is accessible to every student who needs it.