Loading PDF into Web Browser Control

I have a WPF 4.0 applications with a WebBrowser Control. When I navigate to a PDF on the pc, network or on the web it prompts me to open or save it and when I select Open, it opens in a new browser window rather than in the browser control. I have Adobe reader 9 installed, windows 7 pro, 64 bit with IE 9 64 bit. I have complied the applications as x86 as well as 64 and still same results.
Anyone know how to resolve this so that I don't get prompt to save or open and that it opens in the browser control.

The current line of code is Me.WebBrowser1.Navigate(path)

Thanks