Most manufacturers roll the plans rather than fold them. Take them out, roll then the opposite direction, then rub your hands on the rolled plans rapidly until you feel them getting warm. This is usually sufficient to get rid of any excess curling. Tape them to your building surface with masking tape, and cover them with Waxed Paper. Waxed paper won't adhear to most of the glues we use, and is easy to sand off it if does. Its easy to pin through, and will protect the plans. I usually don't copy the plans as its an unneeded expense, and I'm never quite sure the copy machines are truly 1:1.

Brad