Does anyone here know of any ways you can store files in a PDF file without having it display in the PDF? You can do something similar with most office files like .docx files; they’re just .zip compressed so you could add whatever you wanted to a .docx file with an archiver and nobody would suspect a thing. I’m looking to hide an image for a friend to get, like a secret message kind of thing. I don’t need to be able to do it exactly like what I described with a .docx file; I’m just wondering if anyone knows any methods.