A Python script to batch compress PDF files on Windows, MAC, and Linux. Make sure gs and Python are in PATH before running this script.

pdfcompress.py

from __future__ import print_function
import os
import subprocess

root = "."

try:
   os.mkdir('compressed')
except FileExistsError:
   pass   
   
for file in os.listdir(root):
      if file.endswith(".pdf"):
         filename = os.path.join(root, file)
         arg1= '-sOutputFile=' + './compressed/' + file
         print ("compressing:", file )
         p = subprocess.Popen(['gs', '-sDEVICE=pdfwrite', '-dCompatibilityLevel=1.4', '-dPDFSETTINGS=/screen', '-dNOPAUSE', '-dBATCH',  '-dQUIET', str(arg1), filename], stdout=subprocess.PIPE).wait()