Many a times, one feels the need to compare the contents at the top of a document with another part within the same document. MS Word 2007 and later versions allow you to do that using the following ribbon options:
Here are the steps to do that:
View -> New Window: this will open a second copy of the same document in a new window
View -> Side by Side: this will align the view so that both windows are visible at the same time (each taking 50% of the screen)
View -> Synch Scrolling: this will setup synchronized scrolling; so if you move up in one Window, the other Window will scroll with it.
Here are some related tips/ articles on other apps in MS Office: