How to Make PDFs Dark Mode on Android and iPhone
PDF dark mode is a viewer setting, not part of the file. How to turn it on in iPhone, iPad and Android apps, and why it can ruin photos and diagrams.
Dark mode for PDFs is not a document setting — it is something the viewer applies while rendering. That is why it looks different in every app, why it sometimes ruins diagrams, and why the file itself is unchanged when you send it to someone else.
iPhone and iPad
Apple Books is the best option built into the OS. Open the PDF in Books, tap the screen, then the AA menu, and choose the dark theme. It inverts the page rather than just dimming it, and remembers the setting per book.
Files and Safari do not invert PDFs. Turning on system dark mode darkens the app around the document and leaves the page white.
Smart Invert (Settings → Accessibility → Display & Text Size → Smart Invert) works everywhere and is the fallback when an app has no dark mode of its own. It tries to leave images alone, with mixed results.
Android
Adobe Acrobat Reader has a proper night mode in its view settings, and it is the most reliable option because it inverts text and background while attempting to leave images intact.
Xodo offers a night mode too, and is free with no account.
Google Drive's viewer does not invert PDFs; the surrounding interface goes dark and the page stays white.
Force dark in Developer Options applies system-wide inversion. It works, and it treats every app the same way, so results vary.
Why diagrams and photos look wrong
Simple inversion flips every colour, which is fine for black text on white and destructive for anything else: photographs become negatives, and a diagram whose meaning depends on colour becomes misleading rather than merely ugly. Apps that "leave images alone" are detecting image regions heuristically, and the detection is imperfect. If a document is mostly figures, dark mode is often more trouble than it is worth.
Changing the document itself
If you want a dark PDF that stays dark for everyone — a document read on screen by many people, say — that is a change to the file rather than to the viewer. Change PDF page colour sets the background across the document. Be deliberate: it affects printing, where a dark background is both unreadable and expensive in ink.
Frequently asked questions
Why does dark mode work in one app but not another? Because it is a viewer feature, not a document property. Nothing about the file changes, so each app decides independently.
Does dark mode save battery? On OLED screens, meaningfully — black pixels are switched off. On LCD, essentially not, since the backlight is on regardless.
Will the recipient see my dark version? No, unless you changed the document itself rather than a viewer setting.
Why do images look strange in dark mode? Inversion applies to everything unless the app detects and excludes image regions, which it does imperfectly.
