You have probably experienced it before. After a long search, you finally find a PDF file with the content you are looking for, open it in Adobe Acrobat 9 11 Pro, and start to click your way through the conversion process, only to find that it cannot be converted. What went wrong?
Chances are the file is scanned. Depending on the type of PDF you have, either a native or a scanned PDF, the conversion process will differ.
Scanned material does not have the underlying data structure commonly found in electronically generated content, such as a document created in MS Word 2007. Converting a scanned PDF, also known as an Image PDF, thus, requires one extra step when converting.
To get your image PDF file converted, you need to run the Optical Character Recognition (OCR) engine on the file which will transform your scanned document into an electronic character-based file which can then be converted as usual.