Question: How?
Answer: Use Aspose.Words for Reporting Services.
This is a recent (although not latest) feature, but I really love it and would like to take this opportunity to mention it again.
Microsoft Report Viewer out of the box allows export only to PDF and HTML when working in the Local Mode.
We’ve just made a demonstration video about how easy it is to:
Export reports to DOC, OOXML, RTF or WordprocessingML from Microsoft Report Viewer working in the Local Mode.
Question: Ok, what about the Remote Mode?
Answer: Use Aspose.Words for Reporting Services.
This is the original core feature of Aspose.Words for Reporting Services.
There is a demo video for this too. In this mode the reports are generated and exported on the server running Microsoft SQL Server Reporting Services and Aspose.Words for Reporting Services.
Links
See the demo videos here http://www.aspose.com/community/files/52/ssrs-rendering-extensions/aspose.words-for-reporting-services/category1268.aspx
More info about Report Viewer on MSDN http://msdn.microsoft.com/en-us/library/ms251671.aspx
More info about Aspose.Words for Reporting Services http://www.aspose.com/categories/ssrs-rendering-extensions/aspose.words-for-reporting-services/default.aspx