Well, I had an old Sony PR-505 eReader and while it could read PDF's it ccertainly wasn't ideally suited to it. I did usually preprocess them by at least croppi

Well, I had an old Sony PR-505 eReader and while it could read PDF's it ccertainly wasn't ideally suited to it. I did usually preprocess them by at least cropping the margins as much as I could (a program called briss makes this easy). But I think modern eReaders are much better and might be able to zoom in on PDFs. Every other format I came across I converted to ePub using Calibre, which is fairly painless.