I'm a self-published author. This is the default setting for new books uploaded without DRM. It's gated behind an "I understand" checkbox. I plan to allow my books to be downloaded as PDF and ePUB.
It makes sense not to do this retroactively.
It makes sense not to do this retroactively.
Edit: I now realize you might mean in the Amazon KDP UI. I don't see a way to upload your own.