Well, OS X Preview saves your changes even if you quit, and it has some serious issues with radio buttons in documents. It really caused quite the problem with people filling in repetitive forms. The standard "open document, add changes, print, quit" workflow that works in Office products goes very badly on OS X.

You can turn off that auto-saving feature in system preferences. It’s called something like “Ask before saving changes.”

Depends on what it's actually doing. Preview can do actual forms, but it can also "fill" in forms by trying to detect lines and boxes.