IDR - Is there a way to add a Requester if the email is not on the scanned image?

Summary:

We operate with a Shared Service Center model to support non-PO invoice account coding. Most non-PO invoices do not have the Share Service Center support person's email address on the .pdf image. We are trying to determine the best business practice to implement to route these invoices to the correct person.

Content (required):

What is the recommended business practice for adding an invoice requester or email for routing a non-PO invoice imported using IDR if the requester email is not part of the invoice pdf image?

Typically these invoices are not received by AP, could a pdf stamp be put in the image that would be read and imported as the requester email? Or, is it possible to add the email for routing as a Routing Attribute? If we are not defaulting the BU as routing attribute1, can we use that field?