This is a small tool using Tinyscript and PyPDF2 to bruteforce the password of a PDF given an alphabet (defaults to printables) and a length (default is 8).
$ pip install PyPDF2 tinyscript
$ wget https://gist.githubusercontent.com/dhondta/efe84a92e4dfae3b6c14932c73ab2577/raw/pdf-password-bruteforcer.py && chmod +x pdf-password-bruteforcer.py && sudo mv pdf-password-bruteforcer.py /usr/bin/pdf-password-bruteforcer