I used to use that Nikwax waterproofing stuff on my paper maps, and would spread lots of cut up USGS quads all over the floor and go at them with the foam brush. It worked okay, but any real exposure to moisture left you with a soft rag that glued itself together if it dried in a folded state. Moving to real waterproof, tear-proof, durable and reproducible maps has been a true pleasure. Note that I'm talking about hiking and sea kayaking in coastal Alaska here, not Arizona, so other people's needs might be a little different. There is no way I'd go back to a ziploc, but that's my local conditions dictating my gear selection. The plastic maps are so durable I use them on multiple trips and loan them out to other people. I gave my whole series of coastline from Kodiak to Homer to a fellow sea kayaker for the summer. In Photoshop I will add elevation profiles, mileage, and good identified camping beaches (sea kayaking) and so forth. On separate sheets I will make small cards with tide tables, ferry schedules, and whatever other cheat sheets I need. All stuff I can stick in a PFD pocket and soak for 2 weeks with no fear of damage. For tide tables that really get abused, I might even laminate the card so the writing doesn't get scratched off.
Note that Rite in the Rain also makes water-resistant paper. It's okay but will eventually wet-out, and if you are going through the bother, definitely get the Dura Copy (waterproof) stuff.
