I still prefer Adobe Acrobat Reader despite everything, and absolutely hate PDF.js because it seems to take like few seconds to render a page when jumping around, whereas Adobe Acrobat Reader is pretty much interactive. Nevermind the fact that pdf.js has still problems rendering quite many documents I encounter, while Acrobat is basically the de-facto reference implementation for PDFs.

btw if you want quickly some random large scanned PDFs for testing, archive.org is a goldmine. For example here is a scanned 1200 electronics handbook: https://archive.org/details/NationalSemiconductorLinearAppli...

They also do DjVu, so you can see the size difference there. For that particular book, its 58M for the PDF vs 31M for DjVu. So basically half the size.

I use mupdf all the time for PDFs. It's much faster than PDF.js, but still much, much slower than djvu for scanned documents.