When preparing a PDF for professional printing, color accuracy is critical – especially when working with commercial print services that require files in CMYK color mode. Recently, I submitted a print job and needed to ensure that all colors were correctly converted to CMYK, as the print provider explicitly rejected RGB-based files.
To address this, I created a small Ghostscript-based PowerShell script to handle the conversion in a clean and reproducible way.
🔗 GitHub Repository:
Why CMYK Matters in Print
RGB (Red, Green, Blue) is intended for screen display. Printing systems, however, rely on CMYK (Cyan, Magenta, Yellow, Black) inks. Submitting an RGB PDF to a print provider can result in inaccurate colors, unexpected shifts, or even outright rejections. Many providers demand CMYK-only files for guaranteed results.
Solution
The provided script uses Ghostscript to convert PDFs from RGB to CMYK in a single command-line step. It avoids GUI software and enables automated, batch-safe conversion.
Features
- Converts all color spaces to DeviceCMYK
- Keeps vector quality and layout intact
- Command-line based and cross-platform compatible
Usage
./rgb2cmyk.ps1input.pdf output.pdf
A converted, CMYK-only PDF is generated as output. The script wraps Ghostscript with predefined parameters tailored for accurate color space conversion.
For full usage notes, see the README on GitHub.
Summary
This tool ensures that PDFs sent to print services are compliant with CMYK requirements and avoids color conversion issues at the production stage. It’s especially useful in workflows that involve external printers, agencies, or DTP environments.
