how to view pdf file in browser?

There are some nice browsers' plug-ins for this purpose. (I don't think that Adobe's one is one of them, but also usable :-).) So, first of all, I would suggest you simply rely on client-side software on this. This would be more than reasonable. Even if browser does not support PDF (which easily can happen), all browsers will suggest to either save the PDF file or open with some default viewer. Event if no viewers are available, the user will be able to save the file and take care about the viewers later. Event this would not be a great burden for the user, because such viewers are easily accessible.

Of course, you cannot assume that the PDF will be shown in the browser in all cases. If you really want to show it in all cases, you would need to develop some mapping of PDF to HTML and implement creation of the HTML content from PDF on the fly, one the server side, while your ASP.NET code is preparing the HTTP response. This is a pretty difficult and pretty big work. First of all, the problem of creation of mapping would be ambiguous. Why? Because HTML and PDF have very different concepts: HTML is generally fluid, but PDF is totally rigid; this is a kind of "electronic paper", pretty much like a printout. Besides, PDF is pretty much unstructured (pretty much like printout), in comparison with HTML. Overall, this is doable, but I won't encourage you in going into this.

—SA