Setting a Digital Signature for a Document 
Prerequisites
Before you can set a digital signature, you must define the relevant settings in Customizing and store the original application files in the secure storage area.
See also:
Approval Using Digital SignaturesProcedure
You see the Change document: Basic Data
The Digital Signature dialog box appears.
More information can be found under
Result
The digital signature is set once the approval procedure has been completed. Only certain changes, such as the deletion flag, can be made to the document.
The following information on the digital signature can be displayed while you are processing a document (Basic Data screen):