Hiding data in binary images can facilitate authentication of important documents in the digital domain, which generally requires a high embedding payload. Recently, a steganography framework known as the wet paper coding has been employed in binary image watermarking to achieve high embedding payload. In this paper, we introduce a new concept of super-pixels, and study how to incorporate them in the framework of wet paper coding to further improve the embedding payload in binary images. Using binary text documents as an example, we demonstrate the effectiveness of the proposed super-pixel technique.