Verify a signed PDF

Trust states

Open Verify from a signed document's menu and Colophon reports a trust state: a valid signature from a trusted issuer, a valid signature from an untrusted issuer (the case for a self-signed identity), a valid signature whose trust couldn't be evaluated, or an invalid signature meaning the document changed after it was signed.

What verification checks

Verification recomputes the document's hash and compares it against what was signed, and separately checks the signing certificate's chain of trust where one exists. Both checks run locally; nothing about the document is sent anywhere to be verified.

The trusted timestamp

If the document carries a trusted timestamp, verification also reports the time it was signed and whether the authority that issued that time is trusted — so a signature stays meaningful even after its certificate expires. A signature with no timestamp simply doesn't show one; it's still valid, just without independent proof of when it was made. See Digital signatures for how timestamps are added.