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PAC

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

Jobs Accessibility — checks what a machine can check, does not repair View

Since 2010

Operated by axes4 GmbH

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 being PAC 2026 (build 26.1.0.0). It tests a PDF against the machine-verifiable requirements of PDF/UA, assessed through the Matterhorn Protocol, and of WCAG A and AA, then adds quality checks and a screen reader and structure preview for the judgement calls a machine cannot make. PAC 2026 is the first edition to add AI-assisted checks: a model shipped inside the application and run entirely on your own machine, which recognises structural elements such as headings, paragraphs, lists, tables and figures and flags places where the visible layout and the tags disagree.

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 web service.

Worth knowing: It covers the machine-checkable share of the standards: 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, so the PDF/UA heading does not mean every version is fully covered. Its AI adds hints rather than verdicts, and the automated checks cannot judge whether alternative text describes its image or whether a reading order makes sense, so a person still has to review the document. Its offline operation is the vendor's own assurance rather than something we network-tested. Organisational rollout and commercial use have their own terms. It is a checker, not an editor: it finds accessibility failures but cannot fix one, and it has no redaction, page or assembly operations at all. It only covers the machine-checkable share of the standards, and axes4's own FAQ states plainly that a full set of green checkmarks means only that the automatically checkable requirements were met, so a pass is never proof of accessibility and the result is not legally binding. It is Windows-only, with no Mac version released. And the 2026 AI checks are deliberately supporting information rather than official criteria, cannot be individually dismissed, and do not assess alt text or reading order at all.

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
Not verified
Redaction
No redaction feature
Programmatic access
None
Last availability check
Responded in 832 ms 16 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

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 16 October 2026.
Behaviour testing.
We ran this ourselves. The file handling was watched directly.

Sources: pac.pdf-accessibility.org (home, download, check, history, imprint, privacy-policy, resources/general-terms, resources/faq, resources/ai-checks, resources/ai-checks/technical-details-about-ai-assisted-checks, resources/quality-checks, resources/release-notes, resources/technical-documentation-for-system-administrators), all read 2026; www.axes4.com (imprint, shop, desktop-software). Current-release download artifact confirmed directly (PAC_Setup.26.1.0.0.exe, 127,162,624 bytes, HTTP 200); earlier-edition artifact also confirmed still live (PAC_24.4.4.0.zip, 79,450,860 bytes).

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