Final answer:
The principal documents within the ACSA program are the Acquisition and Cross-Service Agreements, which provide the terms for exchange between countries, and the Transaction Agreements, detailing the specific support, supplies, and services to be exchanged.
Step-by-step explanation:
The two principal documents within the Acquisition and Cross Servicing Agreement (ACSA) program are the Acquisition and Cross-Service Agreements themselves and the Transaction Agreements. The Acquisition and Cross-Service Agreements outline the general terms and conditions under which logistics support, supplies, and services may be exchanged between the signing countries. Conversely, the Transaction Agreements are the actual implementation documents that specify the logistics support, supplies, and services to be provided, as well as their associated costs or what will be exchanged in return.