I combined some answers above in inline python that u can add to ~/.bashrc or ~/.zshrc to compile and convert many notebooks to a single pdf file
function convert_notebooks(){
# read anything on this folder that ends on ipynb and run pdf formatting for it
python -c 'import os; [os.system("jupyter nbconvert --to pdf " + f) for f in os.listdir (".") if f.endswith("ipynb")]'
# to convert to pdf u must have installed latex and that means u have pdfjam installed
pdfjam *
}