The date and time are commonly included with a digital signature. A digitally-authorized time stamp gives you unequivocal proof that the contents of any data file existed at a point-in-time and that the contents have not changed since that time, which reduces the risk of an invalid signature. A time stamp is usually fetched from a third-party time stamp authority (TSA), associated with its trusted certificate.

In a signed PDF, the time stamp often appears in the signature field and shows in the signature properties dialog box. If you’ve configured a time stamp authority server, the time stamp will appear on the Date/Time tab of the Signature Properties dialog box. You can check the the certificate of the time stamp authority and add it to your trusted identities list. If no time stamp is successfully retrieved, the date and time from your local computer will be used.

To timestamp a signature when signing PDFs, you have to set your time stamp authority in the Security Settings dialog box.

  1. Choose Document > Certificate Security > Security Settings.
  2. Select Time Stamp Server on the left.
  3. Click Add to add a new time stamp authority. If there are existing TSAs you can edit or remove them.
  4. Select a TSA, and click the Set as Default button. It will fetch a time stamp from the specified TSA the next time you sign a document.

To Add a new time stamp authority:

  1. Click the Add button.
  2. In the Add Time Stamp Server dialog box, enter the TSA name and its URL. If the TSA service requires logging on, you can enter the username and password.


Timestamping a Signature