Open both of the files that you want to compare.
On the View tab, in the Window group, click View Side by Side.

Notes

To scroll both documents at the same time, click Synchronous Scrolling in the Window group on the View tab

If you don't see Synchronous Scrolling, click Window on the View tab, and then click Synchronous Scrolling.

To close Side by Side view, click View Side by Side in the Window group on the View tab.

If you don't see View Side by Side, click Window on the View tab, and then click View Side by Side.