Could you 'watermark' the program for each user (although that wouldn't be trivial), and mention noticeably that the software is watermarked. Not sure if that

Could you 'watermark' the program for each user (although that wouldn't be trivial), and mention noticeably that the software is watermarked. Not sure if that would really dissuade anyone leaking/cracking it though, but it may possibly help determine potentially where the leak/crack came from. There are probably many reasons why watermarking isn't worthwhile though, as you'd then need to have an 'online' system for generating new versions, rather than simply hosting a single file.