In C#, if you want to create a Word document you can use the OpenXML SDK from Microsoft. With that library you have full control of what you do, however, if you are new to the library, you may not like it. To generate a simple document you may want something more practical, like the HTML to OpenXML library.
I created an example Visual Studio 2012 Project (OpenXML SDK 2.5 dependency downloaded automatically via NuGet) in ASP.NET 4.0 that demonstrates how easy it is, thanks to this library, to generate a document. You can save a file on the server or stream it to the user. My example includes both cases.