Please gurus, having completed a year program in Canada and have obtained a year work permit, can one renew this work permit before the expiration date as he's still working? If yes, how many years can one get?

Also, does the company need go through LMIA process in other to renew her employee visa or the employee just needs his employment letter to renew his work permit?

I'm a bit confused here so please I need an advice of one who's sure.

Thanks