PDF4Kindle is a neat little free service that will convert PDFs into .mobi format for reading on Kindle devices. To use the service all that you need to do is upload a PDF and let PDF4Kindle do the rest. When the conversion is complete you can download the .mobi file. The converted file will let you resize the text as you would with any other Kindle document.
Originally from Richard Byrne's blog, Free Technology for Teachers (07/17/13 post).
