In a pinch, you can use an image editor like Photoshop or GIMP; copy the green channel (which should show close to 100% intensity for everything except the printed text) over to the other two channels, and you have a monochrome image with black-ish text on a white-ish background (although I expect OCR will require a bit more contrast-adjustment and cleanup.) Heck, ImageMagick probably has a way to do this in batch processing from the command line.