PDF is not somehow immune to this either — a non-conforming implementation could similarly break what are meant to be forward-compatible extension points by raising an error on an unknown stream or object instead of (as required by the standard) ignoring it.
PDFs certainly can suck, more often those that will only work with abode's software and other viewers I've tried can not.
PDF is not nearly as pleasant under the hood. It's down right lovecraftian.
https://b3n.org/psd-is-not-my-favourite-file-format/
or in the code:
PDFs can be painful as well, more often it's then using abode's pdf viewer, but it's far less common for me. There was a time many years ago when I understood PDF structures better, back when I chose to manually edit and fix a couple of malformed PDFs.
Straight HTML, edit anything everywhere. Super slick.