Batch unlock PDFs whose author forbade copying. This script does not decrypt fully-encrypted PDFs which you can't read at all without the correct password.
%brew install qpdf
Put all the PDFs you want to decrypt in a folder called {input-dir}
./decrypt-pdf.sh {input-dir}
Key command:
%qpdf --decrypt 2008S1.pdf 2008S1-dec-by-qpdf.pdf
brew install homebrew/x11/xpdf