Just found pdftk... it's amazing, comes in a binary distribution for Win/Lin/Mac as well as source.
In fact, I solved my other problem (look at my profile, I asked then answered another pdf question .. can't link due to 1 link limitation).
It can do pdf metadata extraction, for example, this will return the line containing the title:
pdftk test.pdf dump_data output test.txt | grep -A 1 "InfoKey: Title" | grep "InfoValue"
It can dump title, author, mod-date, and even bookmarks and page numbers (test pdf had bookmarks)... obviously a bit of work will be needed to properly grep the output, but I think this should fit your needs.
If your pdfs don't have metadata (ie, no "Abstract" metadata), you can cat the text using a different tool like pdf2text, and use some grep tricks like above. If your pdfs are not OCR'd, you have a much bigger problem, and ad-hoc querying of the pdf(s) will be painfully slow (best to OCR).
Regardless, I would recommend you build an index of your documents instead of having each query scan the file metadata/text.
