Reduce PDF File Size Using Ghostscript
Thanks to this tip, you can reduce (or simply change) the “dots per inch” (DPI) of a PDF file, as I needed to.
Simply install Ghostscript:
sudo apt install ghostscript
…and then use it to change the DPI of your file:
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf
…as the article points out, you can, among other options, specify the DPI settings you want to see in the finished document:
-dPDFSETTINGS=/screen
Has a lower quality and smaller size. (72 dpi)
-dPDFSETTINGS=/ebook
Has a better quality, but has a slightly larger size (150 dpi)
-dPDFSETTINGS=/prepress
Output is of a higher size and quality (300 dpi)
-dPDFSETTINGS=/printer Output is of a printer type quality (300 dpi)
-dPDFSETTINGS=/default
Selects the output which is useful for multiple purposes. Can cause large PDFS.