PPR instructions require mailing of actual passports from countries on the visa-needed list, whilst visa-exempt nationals need only send passport photocopies.
Physical passports get stamped, because IRCC has your actual passport. Makes sense. But what do they do for those in visa-exempt countries? What should they receive? Or is it nothing physical/tangible until they turn up in Canada for landing?
The Certificate of Permanent Residence, referred to in this forum as COPR, which everyone gets. Important document to prove you're a PR until you get your PR card.
(I believe I answered the same question from another person a few days ago.)