Rob McMillan posted an even-par 71 to hold onto second place at 5-under-par 279. American Kyle Kovacs ended one stroke further back at minus-4.
Pettitt, who picks up his first Canadian Tour win, posted just one birdie to go along with 17 pars to cruise to the win.
He was never threatened during the final round as the rest of the field fell off the pace. McMillan rallied late to get back to minus-5.
Craig Kanada closed with back-to-back two-under 69s to finish at 2-under-par 282. Steve Scott, who owns two top-10s in the first three Canadian Tour events, was the final player in red figures as he finished at minus-1.