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 account up to 60 pages |
| 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, 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.
We have not yet run PAC against Taggart’s own test files, so we cannot tell you where the two part company. Until we have, run both, and when they disagree, read both findings rather than 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. Run both. We have not yet cross-checked Taggart against PAC, so where the two disagree, read both findings — and tell us, because that is how the comparison gets done.
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. We have not yet cross-checked Taggart against PAC, so there is no list of known disagreements to consult; tell us about any you find.
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.
Related guides
- How to check if a PDF is accessible: four free checkersCheck PDF accessibility free, online or on your own machine: four checkers against PDF/UA and WCAG, what each catches, and the failures none of them see.
- Acrobat accessibility checker: every rule explainedWhat each of the 32 rules in Acrobat's Full Check means, which PDF/UA condition it matches, and how to fix it — from Tab order failed to Logical Reading Order.
- A screen-reader test script for PDFsTwelve minutes with NVDA or VoiceOver will tell you more than any checker. Here is the sequence, and what each step is actually testing.
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.