The Legal Entity selection criteria can be used to narrow down the resulting output to only those entries associated with a particular Legal Entity.

The Legal Entity Organizations that may appear in the drop-down list will include only those organizations that have been defined to be a "Legal Entity".  This relationship is defined on the Organization >> Edit >> Financials tab (Financial Organization Type >> This Organization is a Legal Entity radio button field).  Inactive Legal Entities will be indicated with a suffix of "(inactive)".  Users having the Purchaser or Purchase Order Viewer role can access documents for the owning organization to which they have access via their role's financial organization access (see Organization Access restrictions).