Sorry for the delay in a response.
If your footer is identical for every page, then you will want to use Stamper.StampPage where your source Page would have your hyperlink, with whatever formatting.
To create the formatted footer you could use our ElementBuilder sample as a starting point, or do HTML to PDF, see this post.
Note though, that if you just add text in a normal URL fashion, then most PDF readers will automatically detect that URL text and make in interactive.
If the above does not answer your question please provide screenshots/PDF showing what you want to get.