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Verify digital signatures

Verifying a signature means to check the signature validity and whether any changes have been made to the PDF document since it was signed.

Verify a signature

  1. Open a PDF document containing a digital signature.
  2. Right-click a signature on the page and then select Verify Signature from the shortcut menu.

    The Validation Status information box shows the results.

  3. Click Properties for more information about the signature.
    1. If the Validity Status claims that the signature is not valid, then you need to verify the signature by contacting the signer. Click Verify Identity to see if the user has entered contact information.
    2. If the contact information is available, you can confirm the signature's origin by matching certificate numbers.
  4. If there is no contact information for a known signer, use alternate means to verify the signature.

Verify a time stamp certificate

  1. Open a PDF document containing a digital signature.
  2. Right-click a signature on the page and then select Verify Signature from the shortcut menu.

    The Validation Status information box shows the results.

  3. In the Validation Status dialog box, click Properties.
  4. In the Signature Properties dialog box, click the Date/Time tab to view the time stamp authority. Then click the Show Certificate button in the General pane if the signer time-stamped from a third-party authority.
  5. If the time stamp authority’s certificate is not trusted, click Add To Trusted Identities. If the time stamp authority’s certificate is not listed, you will have to request it from the signer.

    Select Security > Trusted Identities to manage your list of trusted identities. You can also allow your trusted identities from Keychain to be used during verification.

For more information, see Set signature options.