The text 'Page == NumPages' does not mean anything to WR. You can have '${Page} == ${NumPages}' but in that case both Page and NumPages must be a variable set either with <wr:set .../>, <wr:forEach ... var=...> or using datasource.setMap().
There is no way to test if you are on the last page. Part of the reason why is because inside your if you could have enough text to add another page.
And you cannot have logic like this in your footer because the footer is created once and then is placed on each page. In formats such as rtf and WordML there is not a footer for each page, the footer exists in one place and is displayed on each page.
To have a different footer, you need to have a section break and then for that new section have a new footer.