Comparison
PAC and Taggart: use both
| PAC (PDF Accessibility Checker) | Taggart | |
|---|---|---|
| Vendor | axes4 / PDF/UA Foundation | Codama |
| Platforms | Windows only | Any modern browser; macOS, Windows and Linux |
| Price | Free free of charge, checking only | USD 29/mo or 290/yr Solo, single seat; validation free and unlimited |
| Free checking | Yes | Yes — unlimited, no page cap, no account |
| Hebrew / Arabic reading order | Not handled | Detects visual-order storage and repairs it to logical order |
| Appearance guarantee | Not published | Every fix re-rendered and compared at SSIM ≥ 0.999 |
| Remediation report | No | PDF and JSON, with a timestamped log of every human decision |
What PAC (PDF Accessibility Checker) does well
- The de facto reference checker for PDF/UA conformance
- Free, and its verdict is what most auditors quote
- Includes a screen-reader preview
Where it leaves you
- Checks only — it fixes nothing
- Windows only
- Reports in the language of the standard, not in the language of the fix
Not a competitor
PAC, from axes4 and the PDF/UA Foundation, is the closest thing this field has to a reference implementation. It is free, it is thorough, and when an auditor says a document “fails PDF/UA”, PAC’s verdict is usually what they mean.
It does not fix anything. That is a design decision, and a correct one.
So the comparison is not PAC or Taggart. It is: check with both, fix with one.
Why two checkers is not redundant
Conformance checking involves interpretation. Two implementations reading the same clause will occasionally disagree — about whether a heuristic condition is met, about how strictly to read an exemption, about what counts as “real content”.
When PAC and Taggart agree, your confidence should be high. When they disagree, you have found a case worth understanding, and understanding it is usually five minutes that saves an argument later.
Taggart records known disagreements with PAC and with Acrobat’s checker in its rule file, with the reasoning, rather than quietly picking a side.
What Taggart adds
A fix path. PAC tells you a TH has no /Scope. Taggart writes it, and prints what it wrote.
Plain language. PAC reports in the language of the standard. Taggart reports in the language of the fix, plus what a screen reader actually does when the condition is present.
Right-to-left. PAC has no visual-order detection, so a Hebrew document stored backwards passes it. Why →
Cross-platform. PAC is Windows-only. Taggart’s validator runs anywhere.
What PAC adds
Independence, and the fact that it is what the person auditing you is probably running. Both matter, and neither is something a vendor’s own checker can supply.
The honest summary
PAC is not a competitor, it is a second opinion. Taggart cross-references its findings against PAC and documents any disagreement in the rule file. Use both.
Frequently asked questions
Should I still run PAC if I have Taggart?
Yes. PAC is what most auditors quote, it is free, and it is a genuinely independent implementation. Two independent checkers agreeing is worth far more than either alone, and where they disagree you have learned something about your file.
What if PAC and Taggart disagree?
Read both findings and work out which is right — they usually disagree about interpretation rather than fact. Taggart's rule file records known disagreements with PAC and Acrobat's checker, with the reasoning. Tell us about any you find that we have not recorded.
Can PAC fix anything?
No, by design. It is a conformance checker. It will tell you a Figure has no alternative text; supplying the text is somebody else's job.
PAC is Windows only. What do Mac users do?
veraPDF is cross-platform, free and open source, and covers the same PDF/UA-1 clauses. Taggart's validator runs in any browser. Between them you can get an independent second opinion on macOS without a VM.
Try it against the same file. Taggart's validator is free and unlimited, so you can run your own document through both and compare the findings before deciding anything.
Prices are as published by each vendor and were last checked on . Where a vendor does not publish a price we say so rather than guess. Taggart is not affiliated with axes4 / PDF/UA Foundation.