A Python script to recursively decrypt PDF files using `qpdf --decrypt`, handling files without passwords and overwriting the originals if decryption is successful.

decrypt_all_pdfs.py

#!/usr/bin/env python3
"""
decrypt_all_pdfs.py

Author: Jérémie Lumbroso <lumbroso@seas.upenn.edu>
Date: November 3, 2023

Description:
This script recursively finds all PDF files within a specified directory path,
checks if they are encrypted (without a password), and attempts to decrypt them
using `qpdf --decrypt`. It may require modifications if PDF files are password-protected.

This script is distributed under the MIT License.

Usage:
python decrypt_all_pdfs.py /path/to/pdf/directory

"""

import glob
import os
import shutil
import subprocess
import sys
import tempfile

# MIT License
# Copyright (c) 2023 Jérémie Lumbroso
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.


def detect_pdf_decryption_status(pdf_path):
    # Create a temporary directory
    with tempfile.TemporaryDirectory() as tmpdirname:
        # Copy the PDF file into the temporary directory
        temp_pdf_path = shutil.copy(pdf_path, tmpdirname)
        
        # Construct the output text file path
        text_file_path = os.path.splitext(temp_pdf_path)[0] + '.txt'
        
        # Call pdftotext on the copied file
        stderr_file_path = os.path.join(tmpdirname, 'stderr.txt')
        with open(stderr_file_path, 'w') as stderr_file:
            result = subprocess.run(['pdftotext', temp_pdf_path], stderr=stderr_file)
        
        # Check if the text file is created
        text_file_created = os.path.exists(text_file_path)
        
        # Check if there is output on stderr
        stderr_output = os.path.getsize(stderr_file_path) > 0
        
        # Clean up is handled by the TemporaryDirectory context manager
        
        # Return the final piece of information
        return text_file_created and not stderr_output


def decrypt_pdf(pdf_path):
    # Ensure the qpdf is available
    if shutil.which("qpdf") is None:
        raise RuntimeError("qpdf is not installed or not found in system PATH.")

    # Create a temporary directory
    with tempfile.TemporaryDirectory() as tmpdirname:
        # Copy the PDF file into the temporary directory
        temp_pdf_path = shutil.copy(pdf_path, tmpdirname)
        
        # Construct the decrypted PDF file path
        decrypted_pdf_path = os.path.splitext(temp_pdf_path)[0] + '.decrypted.pdf'
        
        # Call qpdf to decrypt the copied PDF file
        subprocess.run(['qpdf', '--decrypt', temp_pdf_path, decrypted_pdf_path], check=True)
        
        # Check if the decrypted file was created successfully
        if not os.path.exists(decrypted_pdf_path):
            raise FileNotFoundError("Decryption failed, decrypted file not found.")
        
        # Copy the decrypted PDF file back to overwrite the original file
        shutil.copy(decrypted_pdf_path, pdf_path)
        
        # Temporary directory and its contents will be automatically cleaned up


def decrypt_all_pdfs(path):
    # Recursively glob all PDF files in the given directory path
    for pdf_file in glob.glob(os.path.join(path, '**/*.pdf'), recursive=True):
        # Check if the PDF is encrypted
        if not detect_pdf_decryption_status(pdf_file):
            print(f"Decrypting: {pdf_file}")
            try:
                decrypt_pdf(pdf_file)
                print(f"Decryption successful for: {pdf_file}")
            except Exception as e:
                print(f"An error occurred while decrypting {pdf_file}: {e}")
        else:
            print(f"File is not encrypted or already decrypted: {pdf_file}")

            
# Example usage:
if __name__ == "__main__":
    # Use the first command line argument if provided, otherwise default to the current working directory
    path_to_pdfs = sys.argv[1] if len(sys.argv) > 1 else os.getcwd()
    decrypt_all_pdfs(path_to_pdfs)