Sometimes you want to review a document written by a co-worker. Sometimes you want to review that same document written by a co-worker, but you want to make sure you don’t accidentally make any changes to it. Microsoft Word Online and (soon) the Desktop versions have an option to look at the document without being able to make any changes. Here’s how you do it.
Open up the document. Click the Editing button in the ribbon (in the upper-right corner of your window, next to the Share button), and then click Reviewing or Viewing to switch to a different way of looking at the document.
To go back to being able to edit the document, click on the newly-changed-to Viewing button to select an different option to allow you to edit or review it again.