On a Mac go to Library (you need to hold the option key while selecting the Go menu to access the Library)>Application Support>Adobe>Lightroom>Watermark and remove from there.
Windows will have a similar path..
On a Mac go to Library (you need to hold the option key while selecting the Go menu to access the Library)>Application Support>Adobe>Lightroom>Watermark and remove from there.
Windows will have a similar path..