This doesn’t seem usefully true. Some googling for search queries like ‘a/b testing PDFs’ or ‘PDF phone home’ show no one discussing the topic of A/B testing different versions of PDFs, and Wikipedia indicates that only Adobe supports JS and even it produces a popup when you try to phonehome. So any A/B test is going to work on only a fraction of users (how many LWers still use Adobe Acrobat to read PDFs?), and it will alarm the ones it does work on (‘is this PDF spyware‽’).
This doesn’t seem usefully true. Some googling for search queries like ‘a/b testing PDFs’ or ‘PDF phone home’ show no one discussing the topic of A/B testing different versions of PDFs, and Wikipedia indicates that only Adobe supports JS and even it produces a popup when you try to phonehome. So any A/B test is going to work on only a fraction of users (how many LWers still use Adobe Acrobat to read PDFs?), and it will alarm the ones it does work on (‘is this PDF spyware‽’).
Foxit Reader supports javascript, and libpoppler (which powers evince and okular, among others) does as well.
Without something to measure, though, that’s really just a technical curiosity.