PDF tips.
You can use ImageMagick to reduce the size of a PDF by lowering its resolution. From https://apple.stackexchange.com/questions/297417/how-to-decrease-pdf-size-without-losing-quality :
brew install imagemagick
convert -density 72 oldfile.pdf new.pdf
where 72 is the target DPI.
Best option is to use pdfunite, from brew install poppler which also installs other useful PDF tools:
pdfunite another.pdf subdir/others_0*.pdf new_target.pdf
new_target.pdf with the total content of another.pdf and all the individual PDFs under subdir/ named as such.