https://stackoverflow.com/a/7507511/1429450
gs  -o aquinas_physics_4prayercards_en-letter.pdf  -sDEVICE=pdfwrite  -sPAPERSIZE=letter  -dFIXEDMEDIA  -dPDFFitPage prayercards/aquinas_physics_4prayercards_en.pdf