How to convert scanned or image based PDF files.

If your PDF file is a scanned or image based PDF file, the converted file will be a blank document or a picture document. Only the OCR software could convert scanned or image based PDF files to be editable. 

What is OCR?
http://en.wikipedia.org/wiki/Optical_character_recognition

PDF Converter Pro is an OCR software 7-in-1 to convert PDF to Word, Excel, PowerPoint, EPUB, HTML, Image and Text on multiple platforms, which you can extract the text from scanned PDFs to be editable.

To know more details about PDF Converter Pro for Windows version through the link: http://www.iskysoft.com/pdf-converter-windows.html
To know more details about PDF Converter Pro for Mac version through the link: http://www.iskysoft.com/pdf-converter-mac.html