Linux Shrink PDF

With the gs command it is possilbe. 'gs' stands for Ghostcript (PostScript and PDF language interpreter and previewer).

gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=settings -sOutputFile=output.pdf input.pdf

Whereas possible options for PDFSETTINGS are:

/screen

- lowest resolution and file size, fine for viewing on screen

/ebook

- middle was of resolution and file size

/printer

- for printing it

/prepress

- for highquality printing(?)

Source for this:

https://www.techwalla.com/articles/how-to-make-the-output-darker-on-a-pdf-print