I've read the suggestions in the forum. Nothing works. I just now tried starting a new file in the current OS (10.10.5) and even that one opens covering the whole screen.
Window menu > unselect Application Frame. Then each window will float and you can resize smaller. However, when you reopen the file, you may have to resize smaller again.
When Application Frame is turned on it fills the screen. You can resize the Application frame smaller by dragging the edge or corner. It will reopen to that size.
If you don't want to manually resize a layout window when you open or create a new file, you could turn on and size the Application Frame to where you want it on the screen, and then from Preferences>Interface>Panels check choose open Documents as Tabs. The Application Frame is sticky so its bounds always remain the same until you resize it.
So here I've set it to half my screen and any documents open as tabs inside the frame because of the preference setting:
Three open documents tabbed in the Application Frame:
You still have the option of tearing off one of the tabbed documents. Look at the items under Window>Arrange for other options:
Application frame has always been off.
Eureka! The Application -> frame, etc. fix you suggested in this chat box #3 fixes the problem of my having to re-size a document's window every time I open it. Thank you.