Invert PDF Colors (Dark Mode PDF)

Reading a bright white PDF in a dark room is tiring, and many readers have no dark mode of their own. This tool creates a night-reading copy of your PDF: a soft dark mode with a charcoal page and light gray text, a brightness inversion that keeps colours recognisable, or a full photographic negative. The conversion runs in your browser, and the original file is left untouched.

How to use this tool

1. Drop one or more PDF files.
2. Pick a style: Dark mode is easiest on the eyes; "Invert brightness" keeps red as red; Full negative inverts everything.
3. Choose the resolution — 150 DPI suits phone and laptop screens.
4. Download the new PDF and check the page 1 preview.

Formula

Negative: c′ = 255 − c. Keep colours: apply hue-rotate(180°) to the negative. Dark mode: c″ = 18 + c′ × 206 ÷ 255

Inverting R, G and B turns white into black but also turns red into cyan. Rotating the hue by 180° afterwards (the same matrix CSS filters use) brings the hues back, so a red heading stays reddish while its brightness is inverted. Dark mode then squeezes the range so pure black becomes #121212 and pure white becomes #e0e0e0, which avoids harsh contrast.

Example

In dark mode a white page (255, 255, 255) becomes #121212, black text becomes #e0e0e0, and a red title (220, 38, 38) becomes a light red of about (224, 131, 131), which still reads as red on the dark page. A full negative would turn that title cyan (35, 217, 217).

Good to know

The new PDF is made of page images, so it looks the same in every reader but its text cannot be selected or searched, and links stop working. Photos are inverted too, which suits diagrams but makes pictures look like negatives. Keep the original for printing.