Final answer:
The documentation required for setting up a business-to-business VPN in this scenario is the Service Level Agreement (SLA).
Step-by-step explanation:
The documentation required to set up a business-to-business VPN between two organizations in this scenario is the Service Level Agreement (SLA). A SLA is a contract between the two parties that outlines the agreed-upon level of service, including the performance and availability of the VPN. The SLA ensures that both organizations have clear expectations and responsibilities when it comes to security and network management.