A method for preventing overlap during the application of a universal identifier (UID) to a signature document in an electronic signature service is disclosed. The method includes parsing an image file of the signature document to obtain a content vector. A set of addresses of the content vector uniquely correspond with a set of locations in the image. Each value in the content vector indicates content at a corresponding location in the image. The method also includes measuring an overlap quantity for a potential UID location using the content vector to measure the overlap quantity. The method also includes selecting a UID location in the signature document using the overlap quantity. The method also includes applying the UID to the signature document using the UID location.