I use a pretty cheap refurbed 10' Android tablet I got. But I would love to have a big e-ink tablet for further work.
https://www.lenovo.com/us/en/p/coming-soon/lenovo-smart-pape...
On normal sized e-readers (6"), I use koreader [1] for pdfs. It has a good enough “reflow mode” that reformat the pdf to fit the screen.