Best document organizer for Ubuntu

If you have downloaded gigabytes of documents in PDF,html,doc,text etc etc formats then you may be finding it is difficult to dig this heap of files to get what you really want.

I checked for a nice document organizer for Ubuntu on Internet and I got some apps too.but the problem with them was that either it does not support adding files from hard drive (ie only useful while online) or written in java.
My search for a perfect one ended in Referencer, the gnome document organizer.
Features:

* add documents or entire folders
* can index verity of file formats
* tag files
* highlight tags based on number of contents
* thumbnail view of files

Remember, these are features only for an average end-user.Actually Referencer has got seamless capabilities as themselves telling they "designed with the scientist/researcher in mind"!

Homepage:
http://icculus.org/referencer/index.html