3/4 inch plywood laminated with PVC on both sides

I am getting ready to start building a modified Weekender on a Harbor Freight heavy duty 4' by 8' trailer. I have a friend that will give me a sheet of 3/4 " plywood that came from the factory with 1/8" PVC lamination on both sides. Is this a good idea, and if so, what if anything do I need to do to ensure it is waterproof?
Bob Pierce
Bob Pierce