View Documents Side By Side In Word 2010
Microsoft Word has the ability to split the window into two views of the same document. Additionally, you can display two different documents side by side. Doing so is useful if you need to compare them.
First of all, open two documents in Word and then click View > Window > View Side By Side. Note that this option only becomes available when you have more than one document open.
Word resizes both windows so that they fit side by side, occupying an equal amount of space. You can navigate between the two windows using alt-tab, as you would normally, or you can simply click the title bar of the window to make it active.
Synchronous Scrolling
When you display two documents side by side like this, the synchronous scrolling button becomes available.
This button acts like a toggle, so synchronous scrolling is either on or off. As soon as you display two documents side by side, synchronous scrolling is turned on by default and this means that both documents scroll together, regardless of which window you are scrolling in.
When it’s turned off, you can scroll the document in each window independently.
If you have resized any of the windows, you can reset them to their original sizes, occupying half the screen size each, by clicking the Reset Window Position button.
Can I Display More Than Two Documents Side By Side?
Are you crazy?
Two should be enough for anybody 
If you happen to have more than two documents open in Word, clicking the View Side By Side button triggers the display of the Compare Side By Side window. You must use this window to select which document you want to display next to the current one.
