Doc Search is your pro-grade tool for finding PDF documents on the web. Like other pro-grade tools, it comes with a user guide that you should read to use it effectively.
In particular, you should know that Doc Search will find PDF documents on the web which contain the words in your query — it will not attempt to find documents described by the words in your query.
If you run into any trouble with Doc Search or if you have any questions, comments, or suggestions for improvement, please drop me a line.
Aaron D. Parks