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Mofumi PDF

Validate Signature

Check the digital signatures in a PDF: who signed, when, and whether the document changed since.

100% Private — files never leave your device
Upload PDFDrop files here or click to chooseAccepted: PDF Files never leave your device

About this tool

Validate Signature finds every digital signature in a PDF and checks it offline. For each one it recomputes the document hash over the signed byte range, compares it with the hash stored in the signature, and verifies the signer’s cryptographic signature with the certificate embedded in the file.

The report shows the signer, the issuing authority, the signing time, the certificate’s validity period, the certificate chain included in the file, and whether the signature covers the whole file. If content was appended after signing (a later revision), you will see it.

Because everything runs in your browser, the certificate is not compared with an online trust list and revocation (CRL/OCSP) is not checked. A “Valid” result means the document is unchanged and was signed with the key of the listed certificate.

Engines: forge

How to use

  1. 1

    Upload a signed PDF.

  2. 2

    Click Validate signatures.

  3. 3

    Read the report for each signature.

Use cases

  • Received contracts

    Confirm a signed contract was not altered after the other party signed it.

  • Official certificates

    Check who issued and signed a certificate or e-document.

  • Test your own signing

    Verify files signed with Digital Signature before sending them.

Frequently asked questions

What does “Modified” mean?

The bytes covered by the signature no longer match its hash — the file was changed after signing or is damaged.

Why “Covers whole file: No”?

Content was added after the signature (for example another signature or form data). The signed part is still intact.

Is the signer’s identity trusted?

The tool shows the certificate chain but does not check trust lists or revocation online. Trust depends on who issued the certificate.

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