A robust PDF watermarking scheme with versatility and compatibility

Portable Document Format (PDF) files have emerged as a ubiquitous and multi-faceted medium for the dissemination and interchange of information. The watermarking algorithms based on PDF document have spurred much research in academia due to their practical applications in copyright protection, trace-tracking and digital forensics. In this work, we emphasize the unique nature of PDF documents among other multimedia content, and propose a robust PDF watermarking scheme with versatility and compatibility, which is competent in resisting multi-level attacks including text editing, format modification, page extraction, textbox republication, and more. We traverse over the decompressed PDF file for objects related to important elements like text, images and forms, and embed encrypted watermark as a dictionary entry inside the objects. In addition, we have developed a tamper detection algorithm that ensures content integrity and facilitates the identification of tampered areas within the watermarked file. We finally make a comparison between the proposed and existing algorithms, and our algorithm offers high invisibility, scalable embedding capacity, strong robustness. It has excellent compatibility in files with different mediums, content and languages, and it is accessible to diverse file generators and readers. Meanwhile, the method can be applied in various application scenarios like copyright protection, multi-level distribution trace tracking and tamper detection.