Not just web browsers, Acrobat (and probably other PDF readers) have supported executing Javascript in PDFs for decades.
I was joking in 2007, when I was working at Siemens, to my boss, that an Excel cell can contain God and the Multiverse when I put an ActiveX inside that was basically a program I made which would draw a 3D animation based on parameters contained on other cells. Let's say the boss was impressed though for me was just basic OLE.
I see from time to time that younger generations reinvent/rediscover the wheel and I chuckle.
why??? for what possible secure white hat reason could you want to run js in pdfs??!? is nobody sane running the pdf org?
Yeah, I agree.
I first met an interactive PDF when filing a form for some state matter (I live in Italy).
I thought that it was over-engineered and dangerous.
Also, this kind of things tend to gratuitously exclude non-mainstream (especially free) software.