A system encodes a separate assist channel that carries only a small amount of additional information in a hardcopy document to compensate for failure of an OCR system to accurately reconstruct a scanned electronic version of the hardcopy document. After the OCR system produces an interpretation of the scanned electronic version of the hardcopy document, a rewrite system that is guided by the assist channel operates independent from the OCR system to correct decoding errors produced by the OCR system.