This feature is in crawl stage, meaning it is only available to a handful of review databases and/or organizations.
Only review database administrators can perform document deletions.
Document deletion is performed like any other mass action, with documents selected with a search or using the checkboxes in the document list.
The main difference between this action and other mass actions is that once you've selected the Delete documents action, you will see two warning screens.
The first warning screen will give you the option to vault the documents instead of deleting them. You can learn more about vault by selecting the blue button.
The second warning screen will provide any warnings about the particular collection of documents you selected. If there are any colored boxes at the top of the screen, they are alerting you to the fact that some of your selected documents have some complication or concern you should be aware of.
You should read all of the warnings carefully, since you may wish to vault your documents, make changes to which documents are being deleted, or export a list of the documents before deletion.
After you have deleted your documents, you may need to refresh the window for the documents to disappear from your database's list.