https://techcrunch.com/2020/09/23/adobes-liquid-mode-uses-ai-to-automatically-redesign-pdfs-for-mobile-devices/

We’ve probably all been there: you’ve been poking around your phone for an hour, deep in some sort of Google research rabbit hole. You finally find a link that almost certainly has the info you’ve been looking for. You tap it.. aaaand it’s a fifty page PDF. Now you get to pinch and zoom your way through a document that’s clearly not meant for a screen that fits in your hand.

Given that the file format is approaching its 30th birthday, it makes sense that PDFs aren’t exactly built for modern mobile devices. But neither PDFs or smartphones are going away anytime soon, so Adobe has been working on a way to make them play nicely together.