I have been a writer on technical subjects for many years, supplying books and periodicals. I am for the first time writing a major text-book of my own for which I have a publisher in mind. My question is, should I mark each page of the MS I shall be sending him with a copyright watermark as a safeguard?
Not sure what it would achieve, Michael; if a publisher wanted to rip off your work, they only have to type it up themselves, without the watermark.
Your work is your copyright: you could future-proof by emailing yourself a copy of the mss, thus providing datable evidence of ownership; or the old way was to mail a copy to yourself, registered post, and get the P.O. to stamp the opening so that it can be shown to be intact.
If the publisher is reputable, and considering you don't send the entire mss unless it's asked for, you shouldn't have to worry.