# Set signature verification preferences

Before you open signed documents, set your preferences to optimize Reader for validating signatures.

1. Choose Edit > Preferences (Windows/UNIX) or Reader > Preferences (Mac OS), and select Security on the left.
2. To automatically validate all signatures in a PDF when you open the document, select Verify Signatures When The Document Is Opened. This option is enabled by default.
3. Click Advanced Preferences, and then click the Verification tab.
4. Choose the following options:

   When Verifying | These options specify methods that determine which plug-in to choose when verifying a signature. The appropriate plug-in is often selected automatically. Contact your system administrator about specific plug-in requirements for validating signatures.
   Require That Certificate Revocation Checking Be Done Whenever Possible During Signature Verification | Select this option to require certificates to be checked against a list of excluded certificates during validation. If this option isn’t selected, the revocation status for approval signatures is ignored. The revocation status is always checked for certifying signatures.
   Verify Signatures Using | Select an option to determine whether the time that appears in the digital signature reflects the time the signature was validated (Current Time), the time set by the default timestamp server specified in the Security Settings, or the time the signature was created.
   Hide Signature Field Validity Icon When Signature Is Valid | Hides the signature status if the signature is valid, even if the document has changed since it’s been signed (indicated by a green check mark and caution triangle icon).

5. Click the Windows Integration tab, and specify whether you can import identities from the Windows Certificates feature into the list of trusted identities. In addition, specify whether to trust all root certificates in the Windows Certificates feature when validating signatures and when validating certified documents. Be aware that selecting these options might compromise security. This option isn’t available for UNIX.