I second KMC's suggestion: it's the same method I've used when keep track of changes in a script as the rehearsal process went on. Correct page numbers are not just important for actors but the entire production team, especially during tech.
Alternatively, if you don't want to type the whole thing up and have access to a photocopier, you can cut the script in pieces and write page numbers on them, then run it off on 8.5x11 paper.