Owners of the document or file can remove a shared member. To remove a member from viewing a private file, click on the icon and a pop-up will appear with the list of shared members. Hover over the name of the user you wish to remove until a appears. Click on the to remove the user.
Note that the user who created or uploaded the file will not be able to be removed from the list of shared members.
Users will need view and edit permissions in documents to remove a shared member. Depending on the settings of a user's project permissions, they may be able to view all document entities, or just a subset of them. Folders and files marked as public are viewable to any users with view access to the Documents section, so it will not have shared members.