Implementing "View as HTML" for Word and PDF documents on an intranet

I am looking for a way to implement "View as HTML" (as seen in e.g. GMail)开发者_JAVA技巧 for Microsoft Office and Adobe PDF documents stored in an intranet. Can anyone recommend approaches for this?

The intranet consists of multiple .NET sites, so I would prefer a .NET library (one that doesn't launch MS Word on the server) for this capability, but any kind of arrangement is welcome.