Browser DLP - Screen Watermark Protection feature gives admins the ability to inject a watermark to any web page in a Custom URL Group. Screen Watermark Protection can be activated for any Custom URL Group in any policy under Web Filters TAB. Action for the Custom URL Group should be selected other than "No Act" or "Block" to enable selection option.
Watermark ID of any user can be seen in the details of a user in the Users menu.
Also, IDs can be searched in the Users list, using the Search User search box.