Print preview should open at the same size (and same window, optimally) as your primary application. If a user has chosen to keep the application at a certain spot on the screen, overriding their decision will not make them happy. While your application as a whole should remember how big it is, I do not believe that your print preview should behave like a separate application with a separate memory.
There are some use cases where that would benefit the user; I'm not disagreeing with the concept. But it's different, and unexpected. The user won't realize that it 'remembered' where they had it before, they'll just be annoyed that for some reason the stupid print preview keeps popping up on their laptop screen when they had moved the app to their second monitor.