Copying Data Assist Pages is never a really good idea, there are too many things that can go wrong.
you can try using Save As to save the file with another name, but you will need to update the forms action so it posts to the correct page, you may need to update the validation so it redirects to the correct page after failure, and there could be other page name references on the page that will need to get updated.
it's safer to recreate the behaviors on the new page rather than saving it as another file.