How to compress PDF file in Linux

I'm using Linux Mint with xsane for scanning documents on my old but still good Canon MX350 printer/scanner. Scans are saved as huge PDF documents (for example 50 MB) and I would like to compress it to consume much less disk space.

Install Ghostscript

apt install ghostscript

Compress the file input.pdf

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output_compressed.pdf input.pdf

Let's break down these options

• -sDEVICE=pdfwrite: Tells Ghostscript to output a PDF file.
• -dCompatibilityLevel=1.4: Sets the PDF version. Version 1.4 is quite old but widely compatible and often allows for good compression. You can try 1.5 or 1.6 for slightly more modern features and potentially better compression in some cases.
• -dPDFSETTINGS=/ebook: This is the main compression control. As mentioned, /ebook usually gives a good balance.
• -dNOPAUSE -dQUIET -dBATCH: These make Ghostscript run silently and non-interactively.
• -sOutputFile=output_compressed.pdf: Specifies the name of the compressed output file.
• input.pdf: original 50 MB PDF.

Lossy compression (322x) from 50 MB to 155 KB without any visible degradation is worth to keep cloud (Google drive) costs low.