I’m assuming the alterations were done in connection with a server system, a real system, an official document control system were you have to log in with a user name and password, or even swipe your badge or thumbprint, not some “personal” personal computer. If so, the metadata of that file would contain the ID of the logged in person and the time and date of the alteration. Possibly (likely) the file would also retain a history of each revision since the file was created, what was deleted and what was added with accompanying IDs and time stamps. Even if not, securely archived backups of the file should be producible.
It's possible that Pientka was still working in DC when Strzok/Page edited the original 302. The fact that this guy disappeared so quickly, and has been kept out of the public view ever since, tells me that he knows a lot, but will never be allowed to share it.