By right-clicking the document, and seeing "Rotate clockwise" and "Rotate counterclockwise" in the context menu, along with their corresponding shortcuts?
That's actually a good example of a traditional UI that is designed around a few basic patterns (right click -> context menu, here) that enable discoverability.
That's actually a good example of a traditional UI that is designed around a few basic patterns (right click -> context menu, here) that enable discoverability.