Convert PNGs to PDF (optimize for size)

   1 NAME=whatever-name
   2 # Might want to consider using -normalize, -auto-level, -auto-gamma, -contrast-stretch '10%', etc. Enhances for greyscale documents
   3 convert $NAME*png -level '15%,75%' -auto-level tmp.pdf
   4 pdf2ps tmp.{pdf,ps}
   5 ps2pdf tmp.ps $NAME.pdf

Useful information:

CategoryCheatSheet