Pdf manual search engine how to build it?

Hello friends,

can anybody advice me to build a pdf search engine? I saw many sites are already there. But practically they are not fulfilling the requirements. Is there any way to get it done with customized google results? I mean by showing google's results on the site? I saw another site (pdf manual search engine) with the same concept but I'm not sure whether its making use of Google search results. Please advice me.

Thanks.