As @HarryT stated PDFs are not a good match for 6" eInk screens. You might check out the Sony readers though, I had one a couple of years ago, the PRS-350, which could magnify the screen when the PDF had two or three columns, keep it magnified , and page through the columns. I'm not sure if the newer Sony readers still offer that feature. It only worked like that for multi-column PDFs and it was far from being ideal.