Sometimes, especially in a very long document, you want to see two different parts of the document at the same time.
You can do this by splitting the Word window horizontally and scrolling through the separate panes independently.
With the document you want to review open and set to the view you want to use, drag the Window Split bar into the position you want.
Scroll through the active pane to the part of the document you want to see.
Click in the other pane to make it active, and scroll ...