You can use
http://calibre-ebook.com/ to convert the document to ePub (and for library management in general for non-DRM'd books). The conversion is mostly quick & dirty, though, so the result almost certainly won't look as nice as the original PDF - but at least you'll be able to resize the text to what you want. Lots of options for converting that you can fiddle with to hopefully get decent (as opposed to just readable) output.