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PDF Signature Integrity Checker
Check detached PDF signature bytes, content digests and signed-revision coverage locally, with explicit certificate-trust limits.
PDF with detached CMS signatures
JSON integrity report
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
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How to use this tool
- Choose a local signed PDF.
- Run the signature integrity check.
- Review each signature's byte match, covered revision and certificate dates. Issuer trust and revocation are not evaluated.
- Download the JSON report or reset to clear the file and results.
Examples
Check whether a digitally signed contract's bytes match its embedded signature, and see whether a later PDF revision falls outside that signature.
Limitations
- One unencrypted PDF up to 50 MiB, 10 signature dictionaries, 1 MiB per CMS object, four CMS signers and 32 certificates per signature, and 120 seconds.
- Compressed PDF objects are parsed in a fixed-maximum 256 MiB native engine with a 16 MiB structure-report limit. Damaged structures requiring repair are rejected.
- Checks supported detached CMS byte integrity using WebCrypto. Unsupported or malformed signatures are reported as unverified.
- Matching bytes do not establish signer identity, issuer trust, revocation status, trusted time, legal validity, CAdES/PAdES conformance or allowed post-signing changes.
- Detects signature dictionaries retained in the current PDF object structure. Historical objects deleted or replaced in later revisions are not reconstructed.
- Each signature reports whether later bytes exist. An earlier valid signature does not cover the current file's later revisions.
- The PDF is not modified. Visible handwriting or an image is not a digital signature.
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