Going in and out of canada

I saw your message earlier so spoke to someone who had applied for PR and visitor's visa. He got his visitor's visa approved while waiting for his PR approval.
He is in the US as a foreign student and has no other ties to the US. His US visa will expire in June and I think he wants to travel to Canada in May for a conference.
He had his visitor's visa approved BUT he had only asked for a single visit. Not sure if multiple entry visa will be different.
When he received his visitor's visa, he did get a standard letter saying that he cannot be employed in Canada, etc, etc.
He got a 6 months visa which expires after his US student visa (But also remember that in the US, theres ways of staying in the US after the student visa expires as long as something called the I20 has not expired yet and the student has not finished his degree).

Good luck.