You can make small edits in reading layout view. In addition, if you like to make comments or track changes as you read, you can use the tracked changes and comments feature. If you're using an inking device such as a Tablet PC, you can easily make ink annotations in the margin.

Reading layout view may open showing one or two screens, depending on a number of factors, such as the window size. But if the display is showing two screens and you add comments or tracked changes, then it normally changes to one screen, as shown in the picture on the left.