When you open more than one document, Word opens a button for each in the Windows task bar. You can therefore switch between multiple open documents by doing either of the following:
- Click the document's button on the Windows task bar.
- Click the Window menu and select the document.
If you want to work on two documents simultaneously, open both and choose Window → Arrange All. Word opens both documents and arranges the Windows horizontally--one on top of the other.
You can also choose the Compare Side by Side with command from the Window menu. This arranges both documents side-by-side and synchronizes the two windows so that as you navigate one window, the other moves to the same place in the document. You can control the synchronization of scrolling by clicking the Synchronous Scrolling button in the Compare Side by Side toolbar.