Scaling PDFs with GhostScript under linux

scaleA4pdf

 #! /bin/bash
 # modified from SO: http://stackoverflow.com/a/25932668/786559

 input=$2
 output=$(echo $2 | sed s/.pdf/_scaled.pdf/)
 if [ $# -ne 2 ] ; then
 echo "Bad arguments!"
 exit
 fi

 # assume 0<=$1<=100 (no error checks!)
 xx="595" #width of A4 in post script points
 yy="842" #height of A4 in pps

 ss=$(echo "scale=4; $1 / 2" | bc)
 sx=$(echo "scale=4; ${xx}"'*'"( ${ss}/ 100 )" | bc)
 sy=$(echo "scale=4; ${yy}"'*'"( ${ss}/ 100 )" | bc)
 s=$(echo "scale=4; 1 - $1 / 100" | bc)
 gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dSAFER \
 -dCompatibilityLevel="1.3" -dPDFSETTINGS="/screen" \
 -dSubsetFonts=true -dEmbedAllFonts=true \
 -sPAPERSIZE=a4 -sOutputFile="${output}" \
 -c "<</BeginPage{${s} ${s} scale ${sx} ${sy} translate}>> setpagedevice" \
 -f "$input"