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PAC

Free Windows accessibility checker for PDF/UA and WCAG, with local AI-assisted semantic checks.

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Since 2010

Operated by axes4 GmbH

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Opens the vendor's own site.

Jobs covered

Open a task to see exactly what the vendor documentation supports.

Accessibility Browse all accessibility tools

checking PDF accessibility with PAC, where the current product and quickstart pages document checks against machine-verifiable PDF/UA requirements through the Matterhorn Protocol and WCAG 2.2 AA requirements, plus quality checks and AI-assisted semantic checks for headings, paragraphs, lists, tables and figures. It provides screenshot/visual review, a screen-reader and structure preview showing what a screen reader should read and in what order, summary and detailed reports identifying errors, and support for the human judgement calls that automated checks cannot make.

The scope records accessibility checking, reporting and visual/manual review support; PAC does not repair or edit documents, does not OCR or convert them, and its green results do not prove legal accessibility or semantic correctness because human review remains required

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inspecting a PDF in PAC's desktop checker, where the current product page documents opening a PDF by drag and drop, visually reviewing rendered pages, using the screen-reader and structure preview to see what a screen reader should read and in what order, and viewing summary or detailed reports identifying errors. The scope is limited to inspection, visual review and report/preview display inside the accessibility checker; it is not a general-purpose PDF reader, renderer, editor, OCR tool, converter, signer or repair tool, and it makes no semantic-correctness or legal-accessibility guarantee

Where your files are processed

No server involved

An installed Windows application that the vendor states operates completely offline, sends nothing to the internet or to axes4 servers, and has no licensing system to check in with. Its 2026 AI checks run on a model shipped inside the application, and the vendor explicitly declined to offer alt-text checking because that would have required a server-side model. Strongest documentary locality claim in the accessibility group.

Vendor-stated in three independent places, all re-checked against the current release rather than carried over from 2024. The General Terms open with "PAC operates completely offline.

It does not send any data to the Internet nor to the servers of axes4." The FAQ answers "Does PAC access the internet?" with "No, PAC does not access the Internet in any way", and separately confirms the AI model runs locally and that documents are not used to train it. Documentation for the AI checks adds that the AI runs exclusively on the computer running PAC and does not access cloud services.

Recorded as reported, not probed.

What it does

PAC is axes4's free Windows desktop checker for PDF accessibility. The current release is PAC 2026.1, build 26.1.0.0, dated 25 March 2026, and it runs on Windows 10 or Windows 11 with Microsoft .NET Framework 4.8 or higher.

It checks many machine-verifiable PDF/UA requirements through the Matterhorn Protocol and WCAG 2.2 AA requirements, adds quality checks, and provides AI-assisted semantic checks that recognise structural elements such as headings, paragraphs, lists, tables and figures and flag layout/tag mismatches. It supports visual/manual review with a screen-reader and structure preview showing what a screen reader should read and in what order, and summary or detailed reports identifying errors.

The AI model is bundled and runs locally; the vendor states that PAC and the AI operate offline and do not send documents to the internet or axes4 servers. PAC is a checker, not an editor or remediation tool, and it does not repair documents.

Its separate axes4 siblings are axesCheck (hosted check), axesSense (batch, available hosted or locally installed) and axesPAC (API), not part of this desktop product.

Best for

Accessibility specialists, remediators and public-sector document teams who need a free, offline PDF/UA and WCAG check on Windows, and who would rather not upload documents to a hosted service.

Worth knowing

The current release is PAC 2026.1, build 26.1.0.0, dated 25 March 2026. Supported operating systems are Windows 10 and Windows 11 only, with Microsoft .NET Framework 4.8 or higher; there is no released Mac version, though axes4 says one is in development, and there is no Linux version.

PAC is a standalone Windows desktop application, not a hosted or API product. axesCheck is a separate hosted tool, axesSense is a separate batch product available as a hosted service or local installation, and axesPAC is a separate API; none of those is part of this record. PAC itself has no command-line or batch checking interface: the FAQ says batch use is not supported and directs users to axesSense, and the documented MSI switches are installer options, not a checking CLI.

The vendor states that PAC and its bundled AI operate completely offline and send no data to the internet or axes4 servers; that is vendor documentation and was not independently network-probed. The checks are limited to what a machine can check: full support is for PDF 1.7, PDF 2.0 is best effort, and full PDF 2.0 and PDF/UA-2 support is planned without a release date.

AI results are supporting hints rather than official criteria, cannot be dismissed individually, and do not assess alt-text quality or reading-order correctness. The automated checks cannot judge semantic correctness, alternative-text quality or whether reading order makes sense, so human review remains required.

A full set of green check marks means only that the automatically checkable requirements passed; the result is not legally binding or a guarantee of accessibility. PAC does not edit, repair, remediate, redact, sign, encrypt, OCR or convert documents.

The application is free of charge for all types of applications per the FAQ, subject to the General Terms; no synthetic price is recorded.

Details, and where each comes from

Vendor statements, our own reading of their pages, and the things nobody has established yet, each answered separately. Where we have not confirmed something it says so rather than guessing, and a row nobody has established is greyed out.

Versions covered
Windows
Website
pac.pdf-accessibility.org
Requires an account
No
Watermark on the free tier
Not verified
Maximum file size
Not verified
Batch processing
No
Data residency
Self-hosted
Open source
Not verified
Self-hostable
Not verified
Licence
Free of charge for all types of applications under the axes4 General Terms, as stated in the current PAC FAQ

Free of charge for all types of applications under the axes4 General Terms, as stated in the current PAC FAQ; no public source distribution is offered. PAC is a standalone Windows desktop checker from axes4 GmbH; axesCheck, axesSense and axesPAC are separate axes4 products (hosted check, batch/hosted and API routes), not editions of PAC.

Redaction
No redaction feature
Programmatic access
None
Last availability check
Responded in 1251 ms 21 October 2026

Checked automatically by our own runner, not reported by the vendor. 100% of our last 30 checks got a response.

What the redaction verdict rests on

From the vendor's own documentation, read 22 September 2026. Not tested by us.

What that does not establish

The vendor’s own site was read on 22 September 2026 and contains no mention of redaction, sanitisation, blackout or whiteout. Absence from a vendor’s own material is not proof that a feature does not exist - it may be undocumented, or on a page the reading did not reach - but for a NEGATIVE claim it is the strongest evidence available, and it is weaker than a positive quote.

Recorded as such rather than presented as certainty.

https://pac.pdf-accessibility.org/en

What the vendor says

Claims are labelled rather than repeated as fact. Where we have checked something ourselves, it says so and shows when. Checked means we read the vendor's own page and it says what we recorded - not that we tested the behaviour, unless the note says we did.

  • “PAC operates completely offline. It does not send any data to the Internet nor to the servers of axes4.”

    Checked by us - the source says this Read 22 September 2026

    Confirmed verbatim, and this is the most consequential claim in the tier: it is the one that says a document never leaves the machine. The site is operated by axes4, whose axesCheck uploads documents and whose consent text - verified earlier in this campaign - puts the liability for that transfer on the user.

    So the same vendor publishes both a tool that requires an upload and a tool that states it sends nothing, and the difference is worth knowing when choosing between them. Recorded as the vendor's terms; this is a claim our locality instrument could in principle test against the desktop application, and it has not been tested.

    Standing: Re-read and matched byte for byte

    Check it yourself: the source, the SHA-256, and how we checked
    Read
    https://pac.pdf-accessibility.org/en/resources/general-terms
    From
    the text a browser renders
    SHA-256
    6fd3771efc231b26a7e225c6de6e55818fb2a4317014779fe8732029cb050693

    How we checked

    Re-verified verbatim on 2026-09-22: https://pac.pdf-accessibility.org/en/resources/general-terms re-rendered in headless Chrome with scripts/render-page.mjs and the claim's wording found in the rendered text. Originally verified on 2026-09-21. sourceHash is the SHA-256 of the re-rendered text, held as rv-pac-pdf-accessibility-org-en-resources-general-terms-147d8377.txt.

    What this hash proves, and what it does not

  • “PAC is completely free of charge for all types of applications.”

    Checked by us - the source says this Read 22 September 2026

    Confirmed verbatim: "PAC is completely free of charge for all types of applications." is the answer to one accordion question, and a second accordion on the same page asks the question a commercial user would actually have - "Is PAC also approved for commercial applications and free of charge?" - and answers "Yes". A third, adjacent to it, explains why there is no data processing agreement: the vendor says such terms "are not applicable in substance" and the effort "would be out of all proportion for a product that we want to continue providing free of charge".

    So the claim is corroborated rather than merely stated, and the vendor's own reasoning about the commercial case is on the page.

    Standing: Re-read and matched byte for byte

    Check it yourself: the source, the SHA-256, and how we checked
    Read
    https://pac.pdf-accessibility.org/en/resources/faq
    From
    the text a browser renders
    SHA-256
    0fa4a89afe72c374833129b36afd72618d0d46c91154b78bc3695e5c09d9c270

    How we checked

    Re-verified verbatim on 2026-09-22: https://pac.pdf-accessibility.org/en/resources/faq re-rendered in headless Chrome with scripts/render-page.mjs and the claim's wording found in the rendered text. Originally verified on 2026-09-21. sourceHash is the SHA-256 of the re-rendered text, held as rv-pac-pdf-accessibility-org-en-resources-faq-bb5dda51.txt.

    What this hash proves, and what it does not

Each claim is quoted from the vendor's own pages. This section describes what we have and have not checked - it is not a judgement about anyone.

Sponsorship is distribution, not an endorsement or a promise of search rankings, AI citations, traffic, or sales. This listing is a free entry, compiled from published sources.

Visit PAC Report a problem

Related reading

Other tools from axes4 GmbH

  • axesCheck - Free browser-based PDF/UA and WCAG accessibility checker that needs no installation.
  • axesPDF - Windows desktop accessibility checker and fixer for tagged PDFs, with PDF/UA machine checks and one-click repairs.

axes4 publishes PAC and its site, and has maintained PAC since 2023. PAC itself has existed since 2010. Source: pdf-accessibility.org imprint, published by axes4 GmbH , read 2026-10-16.

How this record was put together

Editorial review.
No editor has signed this record off. That is not the same as nothing having been checked, and the lines below say what has.
Source reading.
2 claims taken from the vendor's own pages, read between 22 September 2026 and 22 September 2026.
Website availability.
The vendor's site was last checked on 21 October 2026.
Behaviour testing.
We ran this ourselves. The file handling was watched directly.

Sources: https://pac.pdf-accessibility.org/en (product), /en/download (2026.1, 26.1.0.0, 25 March 2026, Windows 10/11, .NET Framework 4.8+), /en/resources/faq (free, offline, no CLI/batch, no Mac, legal caveat), /en/resources/general-terms (offline and licensing terms), /en/resources/quickstart-guide/introducing-pdf-accessibility-checker-2026 (PDF/UA, WCAG 2.2 AA, quality checks), read 2026-10-16.

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