I print the paper if I am trying to learn something from it. That way I can easily takes notes on it, bring it with me wherever I go without worrying about battery time or tech issues. No distractions :)
I hear good things about the eink device Remarkable though.
iPad Pro (11") with Scrivener + GoodReader in side-by-side mode. I read the text in GoodReader and make notes in Scrivener (Scrivener can also show both the PDF and the notes side-by-side which I've also done).
Just reading, my Kindle Fire 8 works very well for this and is more comfortable to hold than the iPad Pro over an extended period.
I use a generic 10" android tablet, with Zoo for zotero, which syncs my library. And Xodo PDF viewer. That way I can highlight and add notes on the PDF while it's synchronized using webdav. I have tried kindle paperwhite but it just doesn't work.
I bought an iPad Air specifically for this purpose. It is fantastic, and even better with the pencil. I was hesitant at first, but it’s probably my favourite device now. I purely use it to read PDFs and write little notes on them.
I hear good things about the eink device Remarkable though.