Need to attach the final signed documents from Supplier to Purchase Order

Summary

Our requirement is we need attach a final signed legal document from Supplier after the Purchase order is in open status

Content

When we send out Purchase order to Supplier, we have requirement to send legal document with it and once the supplier has signed this document and send it back to us, we need attach to that PO in oracle for our tracking purpose, but this is creating the change order. So, is there a way where we can avoid this change order to initiate when we attach a legal document?

Version

Oracle Fusion R13