Comment by da_chicken

That seems like it would be incredibly fragile. As soon as the receiving party made a change that required re-saving the PDF -- like commenting, highlighting, changing default layouts, saving as a PDF/a, checking PDF/ua, etc. -- it might erase the attached files.

It's also very easy to use pdftk to embed or attach files in a PDF using the methods defined in the PDF standard. No renaming or special knowledge required of the audience.