Unfortunately, Word is a proprietary product not intended to be embedded in 3-rd party products; even though the present-day Word document format is based on the open standard OpenXML, the available solutions for Silverlight are mostly proprietary. You can do your search and see:
http://bit.ly/1wEvybI[
^].
If you really want to byte a bullet still getting limited functionality, you can read Open XML document using Open XML SDK you can obtain from Microsoft free of charge and map the content to, say, Rich Text. Even this component would be 3rd-party. See, for example, this open source product:
http://richtexteditor.codeplex.com[
^].
I would question the whole idea of using Word documents. As you can see, it's not going to be easy. Word documents are not part of W3 standards and look foreign on the Web. Nevertheless, there are many sites using or even editing Word documents on the page. However, this is usually done by mapping the documents onto HTML/XHTML. Indeed, HTML features are much closer to Word than, say, RTF. So, why not using HTML pages for this task, instead of Silverlight?
—SA