Embed authenitcated form

hi everyone, 

just wanting to check, is there any way to embed an authenticated form onto a website - or is linking via the url the only option?  you get the embed code if its an unauthenticated form, but i am keen to try and embed the authenticated form on a similar page.  we have sp online available but am trying to keep the look and feel with the corporate branding the same.

as always, any feedback is appreciated