In a watermarked document printing apparatus, secret information is divided, error correction encoding is performed to each divided pieces of information, and the secret information is converted into a pattern image and embedded in paper. In a watermarked document reading apparatus, after extracting...http://www.google.com/patents/US20070030521?utm_source=gb-gplus-sharePatent US20070030521 - Printed matter processing system, watermark-containing document printing device, watermark-containing document read device, printed matter processing method, information read device, and information read method
