Hello @dspreadbury and @davidbanney,
Happy New Year! Good health, good luck, prosperity and success to both of you and the whole Dorico team!
In general the watermarks in pdf files can be easily removed by using any advanced pdf editor like Foxit PDF Editor.
The better way to protect score sheets, especially in digital format, will be to have our own custom fonts, or glyph editor inside Dorico, that allow us to make custom changes to the music fonts.