The transmission of PDF files is becoming more and more popular on the Internet. In order to ensure that electronic publications are published and distributed on the Internet, copyright transactions occur, or the original watermarked documents are still fully extracted when the watermark information is extracted, a double watermarking algorithm based on PDF documents is designed: robustness against attacks watermarking algorithm and watermarking algorithm to verify the integrity of content. The experimental results demonstrate that the algorithm has good invisibility and robustness.