pdf watermark, positioning help

I've recently been playing around with the idea of automatically updating pdf's that are submitted to our website with our web address. Idealy the text would be a clickable link that is centered and positioned at the very top of the page (although im not quite sure if the clickable link part is even possible with cfpdf or itext).  I've been able to add watermarks using both cfpdf and itext, but the watermarks always seem to be pushed down almost an inch from the top of the page and i need the watermark to be at the very top of the page so that it doesn't interfere with the other text (even though the watermark has an opacity of 85%).  I'm looking for suggestions on how i can:
A. position the text/watermark at the very top of the page.
B. make the text a clickable link.
Any help is greatly appreciated!
Thanks!