A couple of years ago I did a 20,000 computerised accounting document (FR to EN)for which the client had provided their own internal glossaries which I returned, as agreed. I can recall certain terms used as they have reappeared in other jobs done since then as some of the terms were common in the field.

A Purchase Order (PO) is just another term for an order (ordre d'achat, commande) that has been placed for goods and that the Vendor has authorsied provision of the goods speciified therein.

PURCHASE ORDER RECEIVER = the person in charge of receiving purchase orders (PO). This is part of the purchasing management process (la gestion des achats). Purchase requisitions (demandes d'achat) are made subject to approval by a designated person (approuveur) and then a template (modèle) is put together from which a PO is prepared. Then it is the turn of the PO to go through an approval procedure. Assuming all is approved, the buyer can receive the delivery. As I understand the process, the buyer is the Purchase Order Receiver, (le Réceptionnaire Commandes OU Récpetionnaire PO), as I recall having seen PO used in the original French documents).

OPENED LINE ITEMS OF PURCHASE ORDER :
(Articles PO d'une ligne de commande ouverte). Not absolutely sure of this one. I think it means that the transaction is open, ie not yet paid for or where payment is still to be collected when the accounting period ends at some future date. Line will become closed once paid.

Hope this goes some way towards helping you find the temrs you need.