Hello. I don't see where one can easily add a watermark to a visio document.
I would like to put a watermark, such as "CONFIDENTIAL" on a design done in Visio.
John M Visio MVP commented
The Visio way is to use a background page.
It can be the only background page attached to a foreground page or it can be attached to other background pages. Though a foreground can have only one background page, A background page can have a background page, so in a sense they are layered.
If you use the page properties to center the watermark, you can have the watermark background adjust to the page orientation.