I want to highlet any particular text which exists anywhere in the file when this file open in browser, either formate of this file DOC, XLS,PDF,PPT etc.
what should I do for this

I am not sure, if you can do that to all different formats of files that you have listed. But something I have refered to do it in my development is what I would show guide you here.

http://www.kryogenix.org/code/browser/searchhi/

I didn't actually test this out with different file formats, didn't get that extra time to try that out. I am sure you would try that, as you require it;)

Hope that helps

Cheers!

-Vijay G