Do Canadian PR holders need a passport to enter Canada from America?
Not necessarily. To cross into Canada by land or sea a PR card is sufficient. To enter by air they'll need a passport. An airline won't let a person board without one. A PR card should be used at the automated kiosks on arrival rather than the PR's passport. However, invariably the PR will need a passport to leave Canada. The US doesn't accept a Canadian PR card under WHTI regulations and to go anywhere else by air requires a passport.