Time stamping a digital signature

Date and time are by default included with a digital signature. A digitally-authorized time stamp indicates that the contents of any data file existed at that time and have not changed since then. A time stamp is usually retrieved from a third-party time stamp authority associated with its trusted certificate.

If you have configured a time stamp authority server, the time stamp will appear on the Date/Time tab on the Signature Properties dialog box. You can select 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.

Time stamp signatures of a PDF document

Select Security > Time Stamp.

The Time Stamp Service dialog box lists all services you have selected.
Click Add to place a new service.
Select one to be used for the current document.

Manage time stamp authorities

Select Security > Manage Digital Identities.

The Security Settings dialog box appears.
Select Time Stamp Servers in the list on the left.

The list of time stamp servers appears.
If there are existing time stamp authorities, you can set the default one, you can edit or remove them.
1. Select a time stamp authority and click the Set as Default button.
  
  Next time you sign a document, it gets time stamped by the specified time stamp authority.
2. Select a time stamp authority and click Edit to view or change its settings.
3. Select a time stamp authority click Remove to delete it.
Click Add to add and configure a time stamp server.

To add a new time stamp authority

In the Security Settings dialog box described above, select Time Stamp Servers in the list on the left, then click Add.
In the Add Time Stamp Server dialog box, enter the time stamp authority name and its URL. If the Time Stamp Server requires authentication, enter your user name and password, and click OK.