I recently edited a pdf form using Okular (KDE app on Linux - Arch in this case). It was a pretty involved multi page bank mortgage related form. The app that designed this beauty was running on a Mac (can't remember more but I did see Mac in some metadata on it). One field went a bit odd - it would show one number and print another after I got my data entry a bit wrong and corrected it. Clearly a bug.

I passed the form over to Chrome's pdf handler and got the same result. I also passed it through Windows based stuff - I run an IT company. Same result. I did eventually manage to clear the fault.

If I recall correctly it was the day field for date of birth. My DoB is 7th December - I'm a Brit so 7/12. The field wanted 07 for single digit days and I entered 7 followed by the month numbers. So I ended up with 71 in the day field. Field validation was probably not a consideration for an admin in a bank tasked with knocking up a form used by millions of people! If that thing was from IT then they should look for another job.

Anyway - Okular worked the same way as the rest and shared their faults. It did at least manage to look much prettier and work very, very quickly.