A sticky footer is a page footer section which automatically adapts its vertical position to the bottom of the page. You can see it in many modern web sites and it is well supported in CSS (see a CSS script in here).
Well, Axure wise, there are good news and bad news. Or in other words – it is partially supported…
You can define a master footer and make it stick to the bottom of the browser page. It will always appear at the bottom of the browser window.
How to implement the sticky footer:
Add a new master in Axure for the footer layout.
Select the footer and convert it into a dynamic panel.
Right click the dynamic panel and pin it to browser (see image below)