If this image is appended to a PDF document, and you save the file using the Save option, the scanned image remains uncompressed. Lossless compressions can only be applied to monochrome images. To apply lossless compression to a scanned image, select one of these options under the Optimization Options in the Optimize Scanned PDF dialog box: CCITT Group 4 or JBIG2 (Lossless) for monochrome images.
Also, input resolution higher than 600 dpi is downsampled to 600 dpi or lower. If you select Searchable Image or ClearScan for PDF Output Style, input resolution of 72 dpi or higher is required. Acrobat scanning accepts images between 10 dpi and 3000 dpi.
