The Microsoft WebBrowser control is
Adobe doesn't recommend or support
Direct embedding of the AcroPDF control directly into the form itself is supported and this is documented in the Acrobat SDK. See the chapter entitled "Acrobat Interapplication Communication" and specifically the description of the AxAcroPDF object in the Interapplication Communication API Reference. This mechanism is supported in both Acrobat and Reader.
Acrobat allows other ways to make PDFs available within your own application and these are also described in the Acrobat SDK. These are documented here.