How to disable Print Screen shortcut

You can try changing it via

System Settings → Hardware / Keyboard → Shortcuts → Screenshots → Take a screenshot

To disable the shortcut, click the row so that it shows "New accelerator" as shown below and then press the backspace key.

I disabled it with prejudice, because every cursor key event popped up the screenshot dialog and gnome-screenshot is the culprit. I'm mostly using LXDE and couldn't find where this is configured - the usual Linux problem - so I delete /usr/bin/gnome-screenshot and replaced it with a executable file with just # in it. This may not be efficient but does the job.