menu Insert -> Page
set it to be a background page
on this page create a text box, put the word Draft into this box, and
set the font size to suit.
Go to the page to which you want the watermark, menu File -> Page
Setup -> Page Properties
and set the new background page.
I have previously added very large red text "Draft" over the top of my page,
then assigned it to a layer that is non visible, but printable. Then you
only get it it on print.