You can use google docs for this purpose. it will let you open any format easily
<iframe src="http://docs.google.com/viewer?url=www.xyz.com/abc.doc&embedded=true" width="600" height="780" style="border: none;"></iframe></iframe>
give its runat property as server ,and provide an id for this ,after that you can bind it easily from you codebehind.
https://docs.google.com/a/ati-erp.com/viewer[
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