Sorting through windows that are grouped together
If you're in the app where the document is, you can use App Exposé to show just the windows of the current app, nicely spread out on the screen. I've got App Exposé set to a four finger swipe down, but I'm not sure that it's the default. You can find the settings in System Preferences -> Trackpad -> More Gestures (or similar if you've got a Magic Mouse, I would guess).

You can also press F10 to trigger App Exposé.