Here is an update of the python 3 beta to include the ability to use OCR to get the ISBN from scanned PDF files. I've tested it on Windows and Linux. It requires
Tesseract to be installed for the OCR to work. If it is not installed the plugin will work the same as before.
Windows binaries of Tesseract are
here. You will need to add it to your PATH as the Windows Tesseract installer does not do this.