You may want or need to work with PDFs on devices other than a computer. If that is the case follow the links below for recommendations on apps and sites you may try.
PDF Annotation Apps
SmallPDF - This site offers a number of PDF conversion tools allowing a person to convert to and from PDF to a number of different formats for free.
Zamzar.com - This site allows a person to convert to PDF (and other formats) for free.