Make a big pdf smaller from the commandline using ghostscript

smaller_pdf.sh

#!/bin/bash

if [ $# -eq 0 ]; then
    echo "Usage: $0 <filename.pdf> [filename2.pdf …]"
    exit `false`
fi

gs=`which gs`
if [ $? -ne 0 ]; then
    echo "gs not found."
    exit `false`
fi

for file in $@; do
    if [ ! -f $file ]; then
        echo "$file not found."
    else
        $gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=SMALL__$file $file
    fi
done