This is not really a technical question, but more an organizational one.
It depends on how the credentials for the signature are set up; if it is depending on the login, you would provide the according credentials to anyone who may sign.
In fact, it might be an idea to establish a digital signature for the according role in the workflow, and give the persons allowed to sign the needed access (if a signature card is used, then have that card at a central location and provide the access code to the people allowed to use the card).
Hope this can help.