Watermarking a score

[Raphael Mankin]

ISTR a thread a few months back on how to watermark a score, but I 
cannot now find it either in my files, in the snippets wiki or with a 
web search.

My specific case is that I want to print the word DRAFT diagonally, in 
large, thick, pale grey letters as an underlay on every page of a score.

Help appreciated.