Use this submenu to control whether or not to activate the OCR engine for a given selection and conversion:
Selecting "Perform Image-Based Conversion (OCR)" can be useful for PDF files that have been created electronically, but that have damaged fonts or that otherwise convert very poorly. Under certain circumstances, forcing an OCR conversion can provide results where previously a conversion may not have yielded any results.
In some cases, perhaps where a PDF contains mixed image and electronically-created PDF elements, the user may wish to turn off the OCR engine in order to capture only the electronically-created PDF elements – which can result in a much quicker conversion. These users would select the "No Image-Based Conversion (OCR)" option.