Using steganography to hide an embedded file in a PDF, which of the following can be used?

Using steganography to hide an embedded file in a PDF, which of the following can be used?

• {object(/(filename), /(filetype)) show == 0}
• << /hideobj << /type (filename)
• << /Embeddedfiles << /Names [(filename)]
• << /Hidefile #! (filename) 

 

EXPLANATION

In PDF language, you would write "<< /Embeddedfiles << /Names [(filename here)]" to hide a file, as the language is designed in such a way that it looks explicitly for "/EmbeddedFiles" to render an embedded file, which is case sensitive. "/Embeddedfiles" without the capital F means nothing and so, the PDF reader ignores it and doesn't attempt to find the file specified.
Other ways of PDF obfuscation can be read about here, too:
https://blog.didierstevens.com/2008/04/29/pdf-let-me-count-the-ways/

SOURCE

https://blog.didierstevens.com/2009/07/01/embedding-and-hiding-files-in-pdf-documents/