Get Smaller, Faster Printing PDFs with Adobe ClearScan
Rick Borstein posted a study about Adobe's ClearScan OCR software which can generate text searchable images that are clear and smaller in size than those with Acrobat's standard OCR tool. The standard method overlays invisible searchable text over the original image. An image of about 300 dpi will be 15 KB to 40 KB per page. The image slows down printing and appears clearly different than a PDF created from an electronic document.
Starting with an image only 78 page PDF of 1.13 MB, Borstein found that ClearScan generated a searchable image of 401 KB in the same time the standard OCR tool took to generate an image of 1.24 MB.
ClearScan works by generating a custom font for scanned images, rather than attempting to match them to a library of fonts.
According to Borstein, OCR quality in ClearScan matches that of standard OCR. It does have the disadvantage of disabling the touch-up text tool.
It's possible to go from a searchable image to ClearScan text, but not vice versa.
My own experiment shows how ClearScan sharpens the font.