Hi Majin,
A while back I searched for something related and in one of the forums the
use of ghostscript was recommended. I've used it and so far I am satisfied. I
am not savvy, so others forum members might help, but that's how I've been
using it:
In terminal:
gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dCompatibilityLevel=1.4
-dPDFSETTINGS=/ebook -sOutputFile=OUTPUT-FILE-NAME.pdf FILE-TO-REDUCE.pdf
If I'm not mistaken, you could change the size/resolution by changing the
-dPDFSETTINGS variable - please check:
https://www.ghostscript.com/doc/9.23/VectorDevices.htm
