I’m currently in grad school and am reading a ton of PDFs. My iPad and Apple Pencil paired with the app LiquidText has been AMAZING! I actually subscribed to their pro plan so that my papers and annotations would sync between my devices.
I can’t stress enough how much use I get out of the combo and how productive it allows me to me reading, highlighting, and taking notes.
I actually have some complaints too but I overlook them! And the customer service was super responsive when I needed them.