One of the better documents search engines I’ve seen is PDFDatabase. Not only does it look good but it’s pretty effective as well. The initial interface of PDFDataabse looks a lot like most of the torrent or rapidshare multi-search engines. You can type in your query and select if you you’re your search results in a specific category. The last 200 searches are also displayed on the site in case you’re just browsing around. Search results can be sorted by size or in alphabetical order. Each result shows the full name of the file, the download link, search tags, and the size of the file. PDFDataabse has it's own crawler and 6.000.000 file database. Database is updated daily. try it now!