A Secure Digital Text Watermarking Algorithm for Portable Document Format (PDF)

Nowadays, with the rapid development of advanced technologies, an illegal copy of digital documents can be easily generated. The Portable Document Format is the most common and widely used text document on the internet. The copyright protection of these documents is a challenging task. Advanced techniques have been proposed in the past but have not delivered the expected results. These techniques are either robust or imperceptible or have a high capacity, but do not maintain the balance between all parameters. Digital watermarking has been used over the past decade to detect forgery and tampering detection, maintain copyright and authentication. This study proposes a novel approach for Portable Document Format based on document page objects. The Special objects of Portable Document Format are used for watermarking without affecting the content of the original document. The proposed technique preserves the imperceptibility and resists against formatting attacks. The watermark information is extracted with high probability, the proposed technique is robust, secured, imperceptible, and embeds 0.22 KB of the watermark in the host document.