To run this:

• pip3 install -r requirements.txt

• $ python encrypt_pdf.py --help
  

  Output:

  usage: encrypt_pdf.py [-h] [-a {encrypt,decrypt}] [-l {1,2}] -p [PASSWORD] [-o OUTPUT_FILE] file
  
  These options are available
  
  positional arguments:
  file                  Input PDF file you want to encrypt
  
  optional arguments:
  -h, --help            show this help message and exit
  -a {encrypt,decrypt}, --action {encrypt,decrypt}
                          Choose whether to encrypt or to decrypt
  -l {1,2}, --level {1,2}
                          Choose which protection level to apply
  -p [PASSWORD], --password [PASSWORD]
                          Enter a valid password
  -o OUTPUT_FILE, --output_file OUTPUT_FILE
                          Enter a valid output file
  

• For instance, to encrypt bert-paper.pdf file and output as bert-paper-encrypted.pdf:

  $ python encrypt_pdf.py bert-paper.pdf -a encrypt -l 1 -p -o bert-paper-encrypted.pdf
  

• To decrypt it:

  $ python encrypt_pdf.py bert-paper-encrypted.pdf -a decrypt -l 1 -p -o bert-paper-decrypted.pdf
  

  This will spawn the original PDF file under the name bert-paper-decrypted.pdf. The password must be the same for encryption and decryption.