PDF viewers, browsers, web servers, office products, and mobiles are very common targets for exploit development.
However, most vulnerabilities in these applications are simply too valuable to announce to the world. They are generally purchased by offensive cyber operations companies or the government before they could be explained at e.g. Blackhat.
This is one reason it's crucial to have bug bounties. Apple can easily pay more than say, Endgame. If they bought exploits in the same fashion and at the same price point as the defense industry, their security posture would improve tremendously.
The comment surely meant a scenario where the presentation file itself, claiming to tell us about something else, happens to be a PDF exploit that attacks the audience of readers, not that the presentation is about such a vulnerability.
