Unity and Aurgmented Reality

How would I intergrate Aurgmented Reality with unity (free version) for free?

I have had a look at other post but it is confusing and most is for pro users

trying looking at ARToolkitpro from the link below..

http://www.artoolworks.com/products/stand-alone/artoolkitpro/

Qualcomm AR is better than that but it's not released for PC and only for Android devices which will require the UNity to build and test on Android (requre PRO license)