Sometimes you have people listed as reviewers that you don't want on the file anymore. You can delete them as reviewers by following these steps:
Hover over the reviewer's name that you want to delete
Select the reviewer
Select the text "Remove Reviewer"
Confirm the action
Just because you delete a reviewer, it does not prevent the reviewer from being able to access the file. Review links are sharable once they are created. To add extra security to a review link, you can password protect your files by using reviewer permissions.