You will need to use an OCR program (Optical Character Recognition) to turn the images into words, if you wish to edit them. Even better is to scan the text into the OCR software instead of to pdf.

Well known OCR Software:
ABBYY Fine Reader
Omnipage Pro

With this type of software - I wouldn't bother with the free stuff - it's useless. This is one of the times that I would say 'ya gets what ya pays for!'