Is it necessary for landing in Canada once more after getting a?
Yes. It is mandatory step that you will have to complete. There are multiple ways of doing that. One is by actually going out of country and coming back. Second and easiest way is to do flag polling at Canada -US Border. Just google the term flag polling for Canada PR and you will find what you need to know. Last option is by booking an appointment and going at government authorizatized centre. Since centres are very limited, wait time is too much.