your PR card will be sent to your mailing address (i.e. your home) by regular mail.
There is no problem when leaving Canada without PR card, but there's a big issue to enter Canada without PR card.....so when you need to ask your relatives/friends to mail the card back to you by means of security post, then you can enter Canada with PR card.
In fact the airline has the right to let you boarding or not if you don't have PR card as eTA already effective. For those landed PR cannot apply eTA. Better to wait the PR card arrived in order to go back Canada