Canadian Citizen short exiting PuDong Airport, no Visa

Hello, My boss is a Canadian citizen and visiting Vietnam at around the end of this month. He needs to do transfer at PuDong airport. He has 7 hours between arrival and departing.
1. Can he exit the airport for several hours? I was told he can do a three-day stay without a Visa?
2. If exiting is allowed, what's your introduction for the say 3-hour trip?
Really appreciate it!
Steven