One could achieve a similar thing using PDF files by utilizing a feature called "File Attachments" [0], [1]. There is nothing insecure about it too. You could

One could achieve a similar thing using PDF files by utilizing a feature called "File Attachments" [0], [1]. There is nothing insecure about it too. You could even need commercial software for it, and could use TeX and friends [2] to achieve the same. [0] https://blogs.adobe.com/insidepdf/2010/11/pdf-file-attachments.html https://blogs.adobe.com/insidepdf/2010/11/pdf-file-attachmen... [1] https://wwwimages2.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/adobe_supplement_iso32000.pdf#G9.1519247 https://wwwimages2.adobe.com/content/dam/Adobe/en/devnet/pdf... [2] http://tex.stackexchange.com/questions/208012/attaching-files-using-plain-tex-pdftex http://tex.stackexchange.com/questions/208012/attaching-file...