ORIGINAL: MinnFlyer
I prefer to cut them. Folding them makes creases
Also it depends on what you want to do with the plan after you build your kit. I prefer to preserve the plan in case I want to build another (or make repairs) in the future. You can either get the plan copied or trace the parts off the plan onto another surface - I use carbon paper and poster board. Also, if you trace all your wood parts onto a sheet you can save that as a cut sheet for future 4*s. This may seem like a great deal of work, but years from now you'll be happy you did this ... you never know how many kits will be around in the near future.
Anyway, that's another option for you.
-MA