I don't know .. I guess the question is poorly worded .. most people will look for documents that are required internationally, to travel during the eligibility period ..
PR card to enter Canada is a 'localized convenience' for Canadian PR's.. it will probably allow you to board a flight to Canada .. I have never done this personally, but some guys are saying so, so ok, we'll bite ..
Just like using a Nexus card or enhanced driver's license to get between US and Canada .. this are based on 'localized treaties/conveniences' .. they are not internationally recognized/binding ..
Just like NAFTA allows you to work easily between US/Canada/Mexico .. the work permits is easy to get for citizens of the 3 countries ..
To transcend those 'conveniences' internationally .. and think of your PR Card as an international travel document, would be wrong I think ..
You can not use your PR card to get into any other country in the world .. and if you find yourself in some remote banana republic, they may want to see your passport as well, or not allow you on a plane to Canada with just PR card ..