Would you read like this?
This is the question asked by Flickr user Ken-ichi.
He posts this comment below his photo: I've been trying not to print papers this semester and read PDFs in Skim instead, which lets you go full screen, rotate, etc. I've found holding my laptop like this actually isn't quite as bad as I thought, though it's better turned 180 degrees if you don't need the power. Also, access to keys is tough for things like annotation, but paging with the space bar is easy.
Here is a link to Skim. (Skim is a PDF reader and note-taker for OS X. It is designed to help you read and annotate scientific papers in PDF, but is also great for viewing any PDF file.)
Here is a link to Ken-ichi's picture on Flickr.