From wikinotes
Viewers
zathura customizable vim-inspired pdf viewer evince lightweight pdf viewer okular heavyweight pdf viewer, supports encrypted docs, signatures pdf.js javascript viewer, embedded in several web browsers
Encoding and Manipulation
ghostscript CLI utility for ps/pdf manipulation pypdf python module for pdf authoring/manipulation poppler-utils cli util manipulate pdfs pdftk cli util manipulate pdfs
File Format
PDFs are composed of boxes, ....
Boxes
mediabox The largest dimension - contains all crop-marks etc for printing. cropbox Where the page should be clipped (in pdf viewer/when printed) bleedbox Where the printed material should be clipped (generally slightly larger than cropbox for print) trimbox The actual width/height artbox seldom used, allows you to crop small componenents from a pdf for printing.
