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.

To get started with the New Administration Experience: 
  1. From your administrator account, in the account drop-down menu, select Go to Admin.
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  2. Click Signing Settings.
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  3. Scroll to Document Formatting and select a format for the time stamp.
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  4. When finished, scroll to the bottom of the page and click Save.
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For more information, check out this help topic