Build a Python PDF Encryptor in 20 Lines

Why a lightweight PDF encryptor is worth having

PDFs remain the de-facto format for sharing reports, statements, and sensitive documents. But most PDFs are sent exactly as they are—unencrypted, forwardable, and readable by humans and automation alike. A tiny Python encryptor gives you a fast way to add a layer of protection before you send anything outward.

Step 1 — Install the only dependency

This encryptor uses PyPDF2, a lightweight library for reading and writing PDF files.

pip install PyPDF2

Step 2 — Create a 20-line PDF encryptor

Save the following script as encrypt.py. It reads a PDF, copies every page to a writer object, applies a password, and saves the encrypted file.

#!/usr/bin/env python3
"""
Minimal PDF encryptor using PyPDF2.
"""

import PyPDF2

def encrypt_pdf(input_pdf: str, output_pdf: str, password: str) -> None:
    with open(input_pdf, "rb") as file:
        reader = PyPDF2.PdfReader(file)
        writer = PyPDF2.PdfWriter()

        for page in reader.pages:
            writer.add_page(page)

        writer.encrypt(password)

        with open(output_pdf, "wb") as out:
            writer.write(out)

if __name__ == "__main__":
    encrypt_pdf("input.pdf", "encrypted.pdf", "your_password")
    print("Encrypted PDF saved to encrypted.pdf")
    

How the script works

The function encrypt_pdf does everything:

1. Load the original PDF
   PdfReader extracts pages without modifying the source file.
2. Copy every page into a writer
   PdfWriter builds a new PDF in memory, giving us full control over output settings.
3. Apply a password
   writer.encrypt(password) locks the new PDF and requires the password on open.
4. Write the encrypted output
   The encrypted PDF is saved wherever you specify—ready to share.

Next steps: strengthen your workflow

This minimal encryptor is a great utility to keep nearby. You can extend it with:

• Batch encryption for folders containing many PDFs
• A GUI wrapper using Tkinter or PySide
• Integration into automated reporting pipelines
• Metadata scrubbing before encryption

For organisations needing stronger access controls, tamper-resistant consent steps, and AI-aware protection, see the PLEX AILock solution.

Related PLEX reading

References & further reading

• PyPDF2 documentation — Official reference for encryption, page manipulation, and PDF internals.
• Real Python — Working with PDFs — Broad coverage of PDF workflows in Python.
• GfG — PDF encryption tutorial — Another simple walk-through using PyPDF2.