Best Device for Reading PDF’s?

E-Ink tablets like Remarkable, SuperNote, Boox, etc.. are good choices since such devices are specifically designed for reading PDF. I've only tried Boox and I think it's good quality.

If you have a Kindle you can email the PDF to the individual email address associated with your Amazon Kindle account. It won’t look as good as on an iPad if the PDF has color or graphics, but it works fine for documents and books.

iPad Pro. Get the big one. Near-full-size A4 and extremely fast page rendering. Don't waste time and money on Android tablets, ePaper readers, and the like-- learn from the thousands I've squandered and just buy the iPad.

An iPad or Android tablet works just fine.