[eschwartz]

calibre is not designed to do "versioning", and Kovid has rejected such suggestions many times already.


You can have an "ORIGINAL_PDF" and a "PDF".
Or you can have a zip/7z/whatever archive with miscellaneous extras.
Either option conforms to calibre's "one of any specific file extension, maximum" restriction.

Or you can use multiple book records.


There are no other options, and I don't anticipate there ever being any other options.


EDIT: Not entirely true, as I mentioned down below, @BetterRed also uses Evernote links for some things. Also works with custom links using metadata templates, I think, to specified folders. I didn't mention that at first, because it exists outside of calibre's library, so, not really quite as helpful/portable.