Optimize PDF files with Ghostscript.

pdfoptim.sh

#!/usr/bin/env bash
# pdfoptim.sh
#
# Optimize a PDF with Ghostscript
#
# Usage
# -----
# 
#     bash pdfoptim.sh input.pdf output.pdf
#
# For example, a PDF file can be reduced from 136.8 MB to 41.2 MB without losing details.

if [[ "$#" -ne 2 ]]; then
  echo "usage: $0 in.pdf out.pdf"
  exit 1
fi

dpi=300
downsample=0.8
in_file="$1"
out_file="$2"

gs \
    -o"${out_file}" \
    -sDEVICE=pdfwrite \
    -dDownsampleColorImages=true \
    -dDownsampleGrayImages=true \
    -dDownsampleMonoImages=true \
    -dColorImageResolution=${dpi} \
    -dGrayImageResolution=${dpi} \
    -dMonoImageResolution=${dpi} \
    -dColorImageDownsampleThreshold=${downsample} \
    -dGrayImageDownsampleThreshold=${downsample} \
    -dMonoImageDownsampleThreshold=${downsample} \
    "${in_file}"