Digital watermarking algorithm based on structure of PDF document

With the rapid development of digital product,the copyright protection of PDF documents has become a crucial research topic in the information security field.This paper analyzed the structure of PDF documents and the relative digital watermarking algorithms.In order to solve the problem that some large capacity text watermarking algorithms increase the size of the document,the authors proposed a digital watermarking algorithm based on the structure of PDF document.Considering the characteristics that end-of-line marker cannot be shown in the document,this algorithm managed to embed watermark through replacing end-of-line markers of the cross-reference table with a fixed format.The experimental results show that,the proposed algorithm can not only reach the standard of watermark capacity required by digital copyright protection,but also has good concealment and can resist statistics attack as well.