PDF Dark turns any PDF into a real dark-mode file you can download, share, and reread anywhere. The entire conversion happens in your browser — your file never touches a server. A saturation-based algorithm preserves photos and charts in their original colors while darkening the rest. Output is a standard PDF (not a viewer toggle), so it stays dark on Kindle, iPad, Acrobat, anywhere. Free, MIT-licensed, no signup, no ads.