A watermark tells the reader what they are holding before they read a word of it, and discourages a draft being passed on as final.
Around 20 per cent opacity at a diagonal angle is the usual choice. It reads clearly without fighting the text underneath.
A single large mark in the centre is right for status words like DRAFT. Repeating it across the page is for discouraging reuse, because it cannot be cropped out without damaging the content.
The watermark becomes part of each page. Anyone can still remove it with the right software, so treat it as a clear label rather than security.
CONFIDENTIAL is the default, and the same settings work for other words. DRAFT marks an unfinished document, COPY marks a duplicate, and NOT FOR DISTRIBUTION is clear about what is expected of the reader. The text can be up to 40 characters.
Keep the colour grey for a quiet mark and use red for a draft that must not be mistaken for a final version. Leave the faintness around the default so the page stays readable, and switch on the repeat option if the document will be photocopied or photographed.
Yes, every page of the document.
The PDF tool takes text. For a logo on pictures, use the photo watermark tool.
No.
DRAFT, COPY, SAMPLE, FOR REVIEW ONLY and NOT FOR DISTRIBUTION are all common. Anything up to 40 characters works.