Nice! Btw this guy's CV is awesome :) : https://pjreddie.com/resume/
(On Android)
I don't know I've heard of malware with PDFs, I know probably a stretch on Android and this person/HN probably not really a concern. Still don't like auto-download unless expecting one. But I get it was the lack of a browser PDF displayer. Maybe he isn't running PDF.js or whatever that is you run to display pdfs on your site.
(Sorry for so much text, TL;DR I'm afraid of what I don't know) I think I'm secure, but am I really secure?