How do I include a time stamp along with the date signed on document?

You can add a time stamp to the Date Signed field. You configure the Date Signed field from the new administration view.
 
  1. From the top menu bar, select Settings.
  2. Click Signing Settings.
  3. Scroll to Document Formatting and select a format for the time stamp.
           admin-signing-settings-select-date-signed-format
  1. When finished, scroll to the bottom of the page and click Save.
For more information, check out this help topic