Once you send your presentation out for review, reviewers edit it using the markup feature so that you can see what they've changed.
After you receive the edited presentations back from reviewers, you have the ability to compare the various versions of the presentation and merge all of the revisions and comments into the original presentation.
When you compare and merge presentations, PowerPoint shows the differences between them as markups. You can accept and reject one or all markups or revisions. The Markup command on the View menu allows you to track changes made to your presentation by using call-outs within the presentation. These call-outs show changes in detail without obscuring the presentation or affecting its layout. They also give you a more visible and comprehensive view of the changes that have been made.
Each change made in PowerPoint is marked with a call-out box that contains the reviewer's name / initials , the date (on comments only), and the details of the actual comment or change. PowerPoint uses a different color call-out box for each reviewer, so you can quickly identify who made the change.
You can use the Reviewing toolbar to track, accept, and reject revisions. The Reviewing toolbar gives you a variety of views and options when reviewing presentations. The table on the right lists the Reviewing toolbar buttons and a brief description of each.
As you review the comments and changes, you can accept or reject them one at a time or all at once. When you accept a change, PowerPoint deletes the text or inserts it into the presentation, as appropriate. When you reject a change, PowerPoint restores the original text.
When you are comparing and merging changes, you can also open the Revisions task pane to easily identify the changes a reviewer has made to a presentation. You can see a list of the changes made by a given reviewer or get a graphical representation of the changes via the Gallery tab. A list menu makes it simple to apply or unapply changes that the reviewer has made.