Bulk decrypt multiple PDF files
I'd use a third-party utility named qpdf that can be compiled from source, or installed via Homebrew, i.e.:

brew install qpdf


Then change directory to where the encrypted PDF files are, assuming they are in a directory by themselves, and use the following compound command, e.g.:

for f in *.[pP][dD][fF]; do qpdf --decrypt --password=password "${f}" "${f%.*}-decrypted.${f##*.}"; done