If you know your PR card will expire while you’re travelling outside Canada, you should apply for a new one before you leave. You can’t have a third party mail your PR card to you while you’re outside Canada. We don’t send PR cards to non-Canadian addresses.
If your new PR card isn’t ready before you leave, you can still travel but you need a permanent resident travel document (PRTD) to return to Canada by commercial vehicle. You can only apply for a PRTD from outside Canada.