Reduce size of PDF (compress) using Ghostscript at terminal.
Move the shrinkpdf.sh to your system execution folder (e.g. /bin/ in Linux distro). Give it permissions to execute
chmod +x ~/bin/shrinkpdf.sh
First parameter (input.pdf): filename of the PDF that is to be converted
Second parameter (output.pdf): filename of the converted PDF
Third parameter: The DPI (resolution) for the output PDF. Default value: 72. For more compression, lower DPI is better but the quality will be worse.
Run it as follows:
~/bin/shrinkpdf.sh input.pdf output.pdf
~/bin/shrinkpdf.sh input.pdf output.pdf 100
~/bin/shrinkpdf.sh input.pdf output.pdf 120
If you don't want to install shrinkpdf in the system, just run
bash shrinkpdf.sh input.pdf output.pdf 72
https://bash.cyberciti.biz/file-management/linux-shell-script-to-reduce-pdf-file-size/