downloaded via [coursera-dl](https://github.com/coursera-dl/coursera-dl)

$ coursera-dl -u youremail@whatever.com -p -f "pdf" --path=here/is/path/to_folder --clear-cache machine-learning

to extract all pdfs from all folders recursively

$ find . -iname "*.pdf" -exec mv {} ~/Desktop/machine-learning/ ;

delete all empty folders

$ find . -type d -empty -delete