If you open multiple views of a document or have several documents open, you can tile the windows to see them all at once or stack them to overlap.
Tiled
Stacked
To tile or stack windows:
Choose Tile Windows or Stack Windows from the Window menu.
Tip: The Tile Windows command arranges the document windows horizontally in wide windows. To arrange the windows vertically in tall windows, press the Option key while you choose Tile Windows.