@alexandra Christopher Lawley gives a concise review of what's new here. There's quite a lot and he goes fast so you might want to keep a finger on the Pause button.https://www.youtube.com/watch?v=DMU79aZh_2E
One of the best things SteveJobs did was push Apple away from using AdobeFlash, which has since vanished.
Im not sure about pdf as a format, difficult to edit, but its frequently used even though there are word or opensource alternatives