Contemplations of a Closet Curmudgeon

I understand that e-books can read pdf files, too. Is that correct? When they do do they treat them like a pdf, with all line breaks happening where they were originally, or do they convert them fully to the e-book format? If the former the poetry problem is solved--simply make it a pdf, and if the reader needs a large font size they can slide the window back and forth across the page to see the words at the far end of a line...