Watermarking can help deter unauthorized re-sharing of sensitive information in your Box account. When you turn on watermarking for a file, it places a semi-transparent overlay of the current viewer's email address or IP address (depending on whether the viewer is logged in or not), as well as time of access across the document's contents.
- Right-click on the file, or click on the file's ellipses (...) menu, and navigate to Properties > Watermarking.
- Check the box next to Enable watermarking for this file and click Save.
- Click into the folder containing files you want to watermark.
- Click on the folder's ellipses (...) menu, to the right of the + New button, and navigate to Properties > Folder Settings.
- Scroll down to the section titled Watermarking.
- Check the box next to Enable watermarking for this folder and click Save Changes.
Note: Box Notes, video, audio, flash and 3D files are currently do not support watermarking. If you enable watermarking for any of these file types, the file will be inaccessible to users of any access level.
Source: Box Community