The PDF and Pic options open this document cropped on the sides for maximum size reading, especially on hand help devices. Full Size opens it uncropped for possible viewing, printing, or downloading. This document is in the PDF format, (Portable Document Format), for maximum compatibility.
PDF View is a custom viewer that can be searched, has bookmarks to the content, etc. This is a modified version of a viewer provided by Mozilla, (print & download options removed).
Pic View provides each page as a picture for viewing on devices that may not be able to easily view pdf files.
Full Size View allows viewing, printing, or downloading, but does not come with search, or bookmark options. This is a viewer provided by Google.