Answer:
Turn on file and printing sharing for all networks.
Step-by-step explanation:
Windows has several security features when connecting to a network. In the control panel, you can access to Network and internet > Network and sharing center > Advanced sharing options. There you will see 3 different profiles, one for private networks, one for guest or public networks, and one for all networks.
You should take one of the 2 options. Enable file and printer sharing for all networks, so he can just print without doing anything more. Or keeping the print sharing just for private networks, and adding his new branch office's network to the private networks list.