The landscape of paid OCR solutions is, well, expensive. And the unbiased folks from the tesseract homepage say, "Tesseract is probably the most accurate open source OCR engine available." Tesseract OCR's images, but pypdfocr uses tesseract as an engine to convert whole PDFs. With a few crafty command-line utilities, we can create a watched folder that will automatically OCR any PDF copied into it, and create a nice OCR'ed PDF which you can cut-and-paste text from or search happily. This tutorial is partially based on the one at the pypdfocr page, and I owe much to this launchd tutorial…
Read more about PDF to PDF OCR launchd Daemon: Setting a Watched Folder to Create OCR'ed, Searchable PDFs on Mac OSX
