Word doesn't provide any tools for that and even the PDF in your link could easily be doctored (lots of white space above the notice). In any event, surely the real safeguard is that each party to the contract has their own copy?

A simple-enough solution would be to insert a single-cell table at the bottom of the text, give it a diagonal border (or two), then drag the table's bottom border down to the page's bottom margin.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]