Hi @treep, okay thanks for the additional information. As far as we are aware, the proposal to merge the Tobii Pro SDK and Unity SDK is a new one and we certainly do not have any official guide to do so.
However, Unity does offer the possibility to combine DLL’s from other SDK (such as the Tobii Pro SDK) which should hopefully be enough to get started. They posted a guide to do this online @ https://docs.unity3d.com/Manual/UsingDLL.html
In any event, I am afraid we cannot offer much more advice beyond this as nobody has yet attempted this combination and so we cannot guarantee proper functionality.
As you already have the Pro Licence however, I would encourage you to try and please let us know how you get on!