@harry592: after getting PR card you never need any visa to enter in Canada. However before getting PR card (After landing) you can also go back to your home country but you would need visa again to enter in Canada which is called Permanent resident Travel Document so if you dont get PR card and you traveled back to your home country or any other country then you need to apply PRTD from that country to enter in Canada again.
@p_shar : As far as I know there is no term exist as "landing paper" so I really do not know what is that. When you land in Canada they fill landing information in your COPR letter and stamped that. And thats the only proof that you landed and become Permanent Resident and it s clearly mentioned in that paper that its
Not valid for travel
regards
D