@nprofile1q... @nprofile1q... @nprofile1q... AFAIU it is not a web-based PDF reader. It's a web version of the paper, generated natively from the latex markup (via features of the ACM latex class). I wouldn't say it's a great UX, yet, but I do see the point: PDF is a terrible format for anything other than paper printing. So I appreciate that ACM is trying to move past it for scientific publishing.