Research of Digital Watermarking for Text Document

With the rapid development of computer technology and Internet technology, it is easier to transmit ,copy and distribute the digital text, and at the same time it faces the problem of transmitting illegally and tampered hostility. Digital watermarking based on text document can protect copyright of digital products and prohibit piracy. This paper analyses the algorithms and research actuality of the watermarking on the basis of formatted text document, and discusses the watermarking algorithms with regard to PDF document prevalent in current。Finally it gives the further research directions.