Ghostscript — The Complete Guide: Compression, PDF/A and Rendering to Images from the Command Line
Ghostscript is a PostScript and PDF interpreter that many programs use behind the scenes — including some virtual PDF printers on Windows. Run it directly from the command line and you get a powerful tool for compressing, converting and repairing files, on Windows, macOS and Linux.
Ghostscript
Artifex Software
The engine behind many PDF tools: compress, convert to PDF/A, rasterise and repair PDFs from the command line.
Get it from the vendorWhat you get
- Compression — shrinking a heavy PDF of scanned drawings for e-mail.
- PDF/A — converting to the long-term archiving format.
- Rendering to images — pages to PNG or TIFF at a chosen resolution.
- PostScript to PDF — converting output from older programs.
- Rewriting — re-saving problem files and combining files.
Usage examples
Compress: gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -o small.pdf plans.pdf. Render to images: gs -sDEVICE=png16m -r150 -o page-%03d.png plans.pdf. There are many parameters, so the documentation is worth reading. The licence is AGPL-3.0: free for any use, commercial included, but embedding it in closed-source software or in a service that does not release its source needs a commercial licence from Artifex.
Related tools
For structural repair and decryption — qpdf. For OCR on scans, which also relies on Ghostscript — OCRmyPDF. For compression in a GUI — PDF24.
qpdf
qpdf project (Jay Berkenbilt)
Command-line tool to repair, encrypt and decrypt, merge and split PDFs and inspect file structure — without changing the content.
Get it from the vendor
OCRmyPDF
OCRmyPDF project
Adds a searchable text layer to scanned PDFs — old reports, standards and drawings become searchable.
Get it from the vendor
PDF24 Creator / PDF24 Tools
Geek Software GmbH
Free PDF toolbox: an offline Windows program plus a browser version — merge, split, compress, OCR, convert and a PDF printer.
Get it from the vendor
PDFtk
PDF Labs
Classic PDF toolkit: merge, split, rotate, stamp and fill forms from the command line, plus a simple free Windows GUI.
Get it from the vendorThe bottom line
Ghostscript is the professional engine for PDF processing. The learning curve is steep, but one saved command saves hours.