encryption-decryption.md

Encryption and Decryption of PDFs

PDF encryption makes use of RC4 and AES algorithms with different key length. pypdf supports all of them until PDF-2.0, which is the latest PDF standard.

pypdf use an extra dependency to do encryption or decryption for AES algorithms. We recommend pyca/cryptography. Alternatively, you can use pycryptodome.

Please see the note in the [installation guide](installation.md)
for installing the extra dependencies if interacting with PDFs that use AES.

Encrypt

You can encrypt a PDF by using a password:

from pypdf import PdfReader, PdfWriter

reader = PdfReader("example.pdf")
writer = PdfWriter(clone_from=reader)

# Add a password to the new PDF
writer.encrypt("my-secret-password", algorithm="AES-256")

# Save the new PDF to a file
with open("encrypted-pdf.pdf", "wb") as f:
    writer.write(f)

The algorithm can be one of RC4-40, RC4-128, AES-128, AES-256-R5, AES-256. We recommend using AES-256-R5.

pypdf uses `RC4` by default for compatibility if you omit the "algorithm" parameter.
Since `RC4` is insecure, you should use `AES` algorithms.

Decrypt

You can decrypt a PDF using the appropriate password:

from pypdf import PdfReader, PdfWriter

reader = PdfReader("encrypted-pdf.pdf")

if reader.is_encrypted:
    reader.decrypt("my-secret-password")

writer = PdfWriter(clone_from=reader)

# Save the new PDF to a file
with open("decrypted-pdf.pdf", "wb") as f:
    writer.write(f)