Has anyone answered this questions?  I am also trying to embed a link and I added us.promapp.com to the site collection and it is still not allowing the emded.  

Hi, I've been told this function isn't possible.  I hope nintex will move this up on their priorities list of functions to develop, as it has us thinking about moving our documents out of promapp to be housed in SharePoint. SharePoint search function is a lot better for documents as well.