Why RGB PDFs print duller than they look on screen, the difference between CMYK and RGB, and how to convert a PDF to CMYK free online before you print.
Your design glows on screen, then prints flat and muddy. The usual culprit is colour mode: you designed in RGB, but the press prints in CMYK.
RGB vs CMYK in one minute
RGB (red, green, blue) is additive light — how screens make colour. It can show vivid, glowing tones. CMYK (cyan, magenta, yellow, black) is subtractive ink on paper, with a smaller range. Bright RGB blues, greens and oranges often have no exact CMYK match, so they shift when printed.
Why you should convert yourself
If you send an RGB PDF, the printer converts it for you — and you only see the result on the finished job. Converting to CMYK first lets you see the print colours and adjust before committing. Convert your PDF to CMYK here.
When RGB is fine
Digital-only PDFs (email, web, screen reading) should stay RGB — it is the right space for screens and keeps colours vivid. Only convert to CMYK when the file is going to a press.
Colour is one piece of a print-ready file. See the complete print-ready PDF guide for fonts, bleed and standards too.
Frequently asked questions
Can I convert a PDF to CMYK for free?
Yes — our colour-profile tool converts RGB PDFs to CMYK free, no signup.
Why does my PDF look different when printed?
Most often because it was RGB and the press converted it to CMYK, shifting out-of-gamut colours. Convert yourself to preview the change.
Photo by Andy Brown on Unsplash.