Alternately, if you are using Windows, have just those two programs open. Then right click on the task bar and click on "Show windows side by side". This will neatly divide your screen in two parts with one program on the left and the other on the right.
AND, if you're using Windows 10, you can scroll on either window without clicking in either. Just move the cursor over the file to be scrolled and use the mouse wheel.
Charlie