It’s just paper, right?
Paper sizes are just one of a long list of things we take for granted in our lives. Indeed, many folk who work with paper all the time don’t even question it. That’s fine. We’re all busy.
But there’s some really interesting reading behind the whole A size of papers. The most common size (you probably have a sheet somewhere within an ass’s roar) is A4, which is 297mm high by 210mm wide. Odd measurements? Yep. Is there a reason. Of course!