All the fonts are baked into the PDF, so it should be readable anywhere; if it isn't, please submit a bug report!
But if you're looking for a format that lets you reflow the text, by changing the margins or font or text size, you're out of luck. The only way to write something like that is to bake it in from the beginning. That's easy for pure text, but hard to impossible for technical documents with lots of displayed equations, big hard-formatted boxes of text (ie, algorithms), and the like.
(Boaz Barak managed it by writing his Modern Complexity Theory book entirely in Markdown. The mind boggles.)