Watermarks will not be shown to users automatically. Therefore, you need to switch on the watermark option for one or various user groups. To do this, first go to Settings → User & rights → User management. Select the specific user group and below the 'Media' settings, tick the box 'Show watermark' Don't forget to click the 'Save' button at the right bottom corner of the page.
If the user group should no longer have restricted access to downloads, simply untick the box 'Show watermark' and click on the 'Save' button. The user group will now no longer see watermarks and can download files with a watermark immediately without submitting a request.