We tried to make OpenKM as intuitive as possible, but an advice is always welcome.
Forum rules: Please, before asking something see the documentation wiki or use the search feature of the forum. And remember we don't have a crystal ball or mental readers, so if you post about an issue tell us which OpenKM are you using and also the browser and operating system version. For more info read How to Report Bugs Effectively.
You can preview documents in preview tab or you're thinking in some live edit ?. I don't understanding the purpose of the question ? do you've got problem previewing some kind of documents ? I suggest you take a look at our online demo demo.openkm.com and for example test previewing .pdf or .doc files
Just take a scenario, I have uploaded a file into OpenKM, Now my problem was I want to view the content of that file from product itself.(I mean with document viewer).
I don't understand your problem. OpenKM can preview PDF, MS Office and OpenOffice document from the "preview" tab. You only need to have Adobe Flash plugin installed and OpenKM correctly configured (OpenOffice integration and pdf2swf utility)