Still some good info in these docs.
Linux (and maybe macOS) users can enter the following command into their terminal in order to download all the files at once into a new folder.
wget -r -nH --cut-dirs=1 -A "*.pdf" -e robots=off https://maritime.org/doc/neets/
To Windows users: use a better os lololol xD (honestly though the only way I know of to download them all at once is to download wget :/ )
EDIT: made command shorter