You wouldn't both be a permanent resident AND hold a Canadian passport. You only have a Canadian passport if you're a Canadian citizen and, by definition, if you're a permanent resident (PR), then you're not a Canadian citizen.

If not a Canadian citizen, but a permanent resident, the person will still need a visa to enter the U.S., unless a citizen of a country that is part of the visa waiver program.

If from a VWP country and driving, you have to pull over to the secondary inspection station, fill out a visa application, and pay a small fee. (For us, it usually takes maybe 10 minutes.) You don't usually have to do anything special when flying if from a VWP country.

Canadian citizens, of course, don't need visas to enter the U.S. as tourists.