Had they been converted to PDF via Acrobat (or such like) rather than scanned Images I would have suggested looking at CAM::PDF, however I think you are going to have to OCR each page of each document, since IIRC there won't be any (meaningful) text to parse within the PDF. You may want to start by looking at PDF::OCR (which IIRC uses Tesseract) , or some other OCR module from CPAN.

Check out the code.google page for tesseract-ocr

Update: Added link to tesseract-ocr

Hope this helps

Martin