As network technology advances at a rapid pace, an increasing number of individuals are utilizing the Internet to transmit and receive information. However, copying, altering, and other malicious acts constantly threaten the copyright ownership of electronic documents in this open environment of the Internet. Numerous copyright theft, illegal transmission, information forgery, and other problems are emerging. Moreover, because of the absence of copyright protection methods, PDF file owners often need help to secure the subsequent legal use of their PDF files after uploading them to the Internet. Combining blockchain and data hiding of PDF files for the first time, we propose a blockchain-based copyright protection scheme for PDF files to uniformly handle the problems of copyright authentication, authenticity identification, and copyright disputes of PDF files. First, we propose a new information hiding algorithm based on the incremental update characteristics of PDF, which embeds copyright information in PDF files. Second, the scheme enables users to establish their access control policies via smart contracts and delivers on-chain PDF file proofs, which can be employed to validate the ownership rights of PDF files and track the transaction history of PDF files. We have implemented the system on the Ethereum platform and analyzed its security and traceability. The experimental results demonstrate that the proposed information hiding algorithm possesses robust security and that the copyright registration method is rapid