No. I'm afraid once a document has been signed by all users, then the document cannot be amended. 

You can use the duplicate feature (icon below) which will duplicate the document, containing the same information (which can then be amended/updated) in an un-signed state.

When duplicating document, you also have options to retain or remove manually made changes and comments when duplicating a document by either choosing 'Preserve tracked changes and comments' or 'Accept all changes and resolve all comments' as per your needs and requirements.