Color photo copy is fine. But do not change the page size. Doing so would make at least 2 puzzles unsolvable.
I would still enlarge it.
Scott is correct, however, I don't think he plans to not use the original while playing.
I think having an enlarged copy will allow things to be seen more clearly, etc. but if you have to measure something or cut up pages, etc, you use the original.
Maybe make 2 copies, one larger and one same size, so that you have a copy to pass it along to others when done playing.