Printed document isn't what I was on about. There the default should 100% be about accessibility (and then we just want that by default cause we're used to it).

PDF -> Nope.

.doc(x) -> Sure.

Website, OS, apps (including terminal) -> Sure.

Now regarding PDF I might've tried a long time ago when reading some old document (like CIA about MKULTRA). I don't remember if I succeeded. But there are PDF editors out there. I do think it likely screws layout (esp. larger documents), but that can be true for .doc(x) as well.

I think it would be a smaller issue if it only applied to digital media. Presumably though this applies to all media.

And I can certainly confirm that changing the font of PDF will almost always result in a unreadable mess. Something about how a PDF doesn't have text "blocks" and instead fixes each character making text reflow almost impossible.