There's a difference between exploiting bugs that haven't even been found and spreading malware through a method that's known by pretty much everyone and is still used to spread malware today.

It's also theoretically possible that your system is already infected by some Advanced Persistent Threats but does that happen that often, No, and have people been infected by running random pdfs they found online, Yes.

Tell that to circuit board designers. It's horrible every time a 3d model of a circuit board is added. The component height gives no visual advantage, and it's slow as shit on corporate computers.

I like how Microsoft came up with an obscure extension for screensavers, which is just an .exe in disguise.