The Purchase Order feature is designed to work in concert with Levels and Reorder Form/Report to streamline the ordering process. When creating POs you have the ability to create them for specific stores or leave them unassigned.
Individual PO lines can also be assigned to specific stores or left unassigned, as well. It is possible to have a single PO with items assigned to more than one store and, when using Receive Invoice, ordered items can be re-allocated to different stores.