DocForensic

PDF Signature Validator

Check every digital signature in a PDF, its certificate chain, and whether the file was modified afterward.

A digitally signed PDF carries a cryptographic signature over the bytes present at the moment it was signed. This tool finds every signature field in the document, verifies it against that signature's own covered byte range, checks the signing certificate's chain against a trust store, and rates the overall document Valid, Invalid, Unsigned, or Modified After Signing. It only reads the file; nothing is changed.

Simple workflow

How it works

  1. 1

    Add PDFs

    Add one or more signed PDFs to the list.

  2. 2

    Validate

    Run validation on a file and open its signature panel.

  3. 3

    Review

    Inspect each signer's certificate chain and coverage, then export a validation report.

Frequently asked questions

Does this check whether a certificate has been revoked?

Not in this version. Live revocation checking (OCSP/CRL) needs an outbound network call from the document processor, which this tool does not make yet. Every signature's revocation status is reported as "unavailable" rather than guessed at.

What does "Modified After Signing" mean?

A digital signature only covers the bytes present in the file at the moment it was applied (its byte range). If the file grew past that range afterward - even by a legitimate later signature or form fill - this tool reports it so you know the signed content is not the whole current file.

Is a self-signed certificate automatically untrusted?

By default, yes - it is flagged as self-signed and not chained to any trust store, though its cryptographic validity (whether the signature itself is genuine) is still shown separately. You can whitelist specific self-signed certificates as trusted under Trust Store settings.

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