Re: Document formats
PDF WAS designed with editable in mind. That was always an option.
The point is that it was an option. It became useful because it had an option of "not editable fixed formatting" which no one else offered at the time. That then became the default.
But even with this default "not editable fixed formatting" it was always editable, except that most users (in particular on Windows) needed to buy Adobe software to do it.
(Theoretically, you can package almost anything in PDF. The problem that it is quite messy behind the scenes to do so, so that it is not guaranteed that the recipient can see all of it.)