We have added button on quotation view to revise Purchase order when user want to create new revision.
Users can revise quotations in drft and canceled states. Revised quotations will remain in Quotations menu. If Purchase order is revised we can see Purchase order link on form from which it was revised.
When ever any new revision get created it will add suffix '-R' on Purchase order sequence and revision no of Purchase order. Revision no will get incremented by one every-time when same PO get revised. If we revise PO005 ir will create new quotation PO005-R1 and PO005 will be in revised state where user can not confirm or cancel PO anymore.
Revise Purchase Orders