You can add comments for the slide as whole and to certain parts of text. Simply have either the slide selected from Slides menu on the left or select the text on the slide you wish to comment. Next continue to Review tab and Comments section. Click on “New Comment” to leave a comment. Note that all the comments are numbered. To hide those comments from the view, click on “Show Markup”. To view the comments, click on the same button again. To edit a comment click on “Edit Comment” that is just next to the button “New Comment”. - Office ToDo