18. The watermark embedding apparatus according to claim 17 , wherein the watermark embedding apparatus can be disposed between a document editor and a printer.
17. The watermark embedding apparatus according to claim 16 , wherein said document is a document in printer description language format, and wherein said watermark embedding apparatus further comprises: a printer language analysis unit for performing printer language analysis on the document in printer description language format, and separating a printer command and content of the electronic document itself for further processing; a printer language reassembling unit for reassembling the printer command and the content of the document embedded with the secret message sequence to generate a reassembled printer language document for printing.