When you want to look at two documents at the same time to compare their content, Word will place the documents in adjacent windows. If the documents are similar enough, you can have Word scroll through both of them at the same time, or you can scroll through the documents at your own pace.
In one document, on the View tab, click the View Side By Side button.
If a dialog box appears and asks you which documents you want to view, select the documents you want, and click OK.
If you don’t want the documents to scroll together, on the View tab, click the Window button to expand the window section (if it’s collapsed), and click the Synchronous Scrolling button to turn off the scrolling. Click Synchronous Scrolling again to resume the coordinated scrolling.
Scroll through the documents. When you’ve finished, click the Window button again, and click the View Side By Side button to turn off that view.