Free PDF Accessibility Checkers: Complete Guide

Before paying for remediation, you need to know what's wrong with your PDFs. Several free tools can check your documents for accessibility issues against WCAG, PDF/UA, and Section 508 standards. This guide compares the best free options and explains what they can and cannot detect.

PAC (PDF Accessibility Checker)

According to the official PAC website, PAC is "the globally used, free PDF accessibility checking tool that has been tried and tested since 2010." It's considered the gold standard for PDF/UA validation.

PAC Limitations

According to Colorado State University:

• Windows only: PAC does not run on Mac or Linux
• Cannot fix issues: You still need Adobe Acrobat Pro or another tool to remediate
• Requires manual review: Some checks require human judgment

Download: pac.pdf-accessibility.org/en/download (free, no registration required)

axesCheck (Online Alternative)

According to axesCheck, it is "an online version of the PDF Accessibility Checker (PAC). Quickly and easily check the machine-verifiable requirements of PDF/UA (according to the Matterhorn Protocol) and WCAG (A & AA)."

As Colorado State notes, "For MAC users seeking a solution, axes4 offers axesCheck, an online PDF accessibility checker tool. This alternative provides a convenient workaround for MAC users."

axesCheck Features

• Works in any browser (Mac, Windows, Linux)
• No software installation required
• Matterhorn Protocol validation
• WCAG A and AA checking
• Free to use

Access: check.axes4.com

Adobe Acrobat Accessibility Checker

Adobe Acrobat Pro includes a built-in accessibility checker. According to Adobe's documentation, you can "create and verify PDF accessibility" within the application.

Adobe Checker Limitations

According to a discussion in the Adobe Community:

"Accessibility Check only tests checkpoints that can be verified with automation. There are a couple of prompts for the tester to check things that require manual validation... It's exceptionally limited in what it checks."

Items the Adobe checker leaves out include:

• Color contrast verification
• Incorrect tag types (like a list with all P tags)
• Illogical tag reading order
• Inappropriate or incomplete alt-text quality
• Complex table assessment

As the Adobe Community discussion notes: "The reality is that currently Acrobat doesn't check to any one specific standard 100%, not even close actually."

veraPDF

According to PDFix's tool comparison, veraPDF is "the industry-leading open-source PDF accessibility validator, providing ISO 14289-1 (PDF/UA-1) conformance validation for Section 508 and ADA compliance."

veraPDF Features

• Open-source and free
• PDF/A and PDF/UA validation
• Command-line and GUI versions
• Batch processing capability
• Cross-platform (Windows, Mac, Linux)

Comparison: Which Tool Should You Use?

What Automated Checkers Cannot Detect

According to PDFix, "Checkers and automated remediators primarily focus on technical elements of accessibility, so manual review is still necessary. Every major accessibility standard, like WCAG, PDF/UA, EN 301 549, requires human evaluation."

Issues requiring human judgment include:

• Alt text quality: A checker can verify alt text exists, but not if it's meaningful
• Logical reading order: Automated tools may miss subtle order issues
• Correct heading hierarchy: Semantic appropriateness requires context
• Table header associations: Complex tables need human review
• Color reliance: Whether meaning is conveyed only through color

Best Practice: Combine Multiple Tools

According to PDFix, "Accessibility professionals achieve highest accuracy by combining validator strengths. High-confidence issues flagged by all tools require immediate fixing, while validator disagreements identify gray areas needing expert judgment."

Recommended workflow:

1. Run PAC or axesCheck for comprehensive PDF/UA validation
2. Use Adobe Acrobat's checker if you plan to fix issues there
3. Perform manual review for issues tools cannot detect
4. Test with actual screen readers (JAWS, NVDA) for real-world validation

From Checking to Fixing

As University of Washington notes, "You still need Acrobat Professional to be able to fix any issues found." Free checkers identify problems but don't remediate them.

Options for remediation after checking:

• Adobe Acrobat Pro: Manual remediation (time-consuming for complex docs)
• Professional services: Human experts fix issues ($7-15/page)
• AI-powered tools: Automated remediation with human review ($3-6/page)

AdaRemediation: Check and Fix

AdaRemediation combines accessibility checking with automated remediation:

• Free audit: Upload your PDF and see exactly what's wrong
• Detailed report: Issue counts, risk scores, estimated fix time
• One-click remediation: Fix issues without manual Acrobat work
• Human review: Approve alt text and changes before finalizing
• Compliance validation: WCAG, PDF/UA, Section 508 testing