Well, after a little hour of research, it seems the entire planet is struggling with that. As an object or an embed is considered an application, it will always be on top, no support for styling as this is not part of the page and it doesn't like pretty much all approaches to not show on top. The only way I have seen which is working is to use the Google viewer. But, that involves the user to go across a security content issue and broadcast confidential files to Google. So, this is a no go.

I had assumed with HTML 5, we would have been a little bit ahead than that, especially a PDF, which has been there for years. But, it doesn't seem to be the case.