How to Invert Colors in Sumatra PDF for Night Reading

Sumatra PDF is legendary for its speed, but its minimalist UI hides most appearance settings. If you read late at night or deal with light-sensitive content, you can still learn how to invert colors in Sumatra PDF using configuration files, keyboard shortcuts, and third-party themes. And when a document refuses to cooperate, route it through /invert-pdf-colors for an instant dark-mode copy.

Method 1: Toggle Inversion via Advanced Settings

1. Press Ctrl + K (or go to Settings → Advanced Options)
2. Sumatra opens SumatraPDF-settings.txt
3. Locate the FixedPageUI section
4. Add or edit this block:

FixedPageUI {
    TextColor = #FFFFFF
    BackgroundColor = #000000
    SelectionColor = #5555FF
}

5. Save the file and restart Sumatra PDF

This inverts text and backgrounds for all future sessions.

Method 2: Keyboard Shortcut

Sumatra supports an instant invert toggle:

• Press Ctrl + I to cycle through color modes
• Use Ctrl + L to switch to presentation view, which respects the inverted palette

Method 3: Theme Presets

1. Download community-made themes (search “SumatraPDF themes” on GitHub)
2. Paste the FixedPageUI block from the theme into your settings file
3. Assign different color sets for day vs night reading

Method 4: Per-Document Profiles

If you only need inversion for certain PDFs:

1. Set RememberStatePerDocument = true inside the settings file
2. Open the target PDF and toggle inversion via Ctrl + I
3. Sumatra remembers that state for the specific document while leaving others untouched

Method 5: External Dark Mode via Print to PDF

1. Use Windows’ Print to PDF feature to create a copy of the document
2. Open the copy in Sumatra after enabling your dark theme
3. The print process flattens unusual color profiles that might ignore FixedPageUI

When Sumatra Isn’t Enough

Some PDFs contain embedded bitmaps or annotations that disregard Sumatra’s color rules. Instead of fighting the app, upload the file to /invert-pdf-colors. The browser inverter processes every page via canvas, guaranteeing that even tricky elements—images, gradients, and stamps—flip into night-ready palettes. Download the result and drop it back into Sumatra with your dark theme intact.

Troubleshooting Tips

• Settings won’t save: Ensure Sumatra isn’t running when you edit the config file
• Colors look muddy: Experiment with dark gray backgrounds (#111111) instead of pure black
• Embedded images stay bright: Use the online inverter to re-render the PDF
• Shortcut conflicts: Rebind keys inside the Shortcuts section if other apps grab Ctrl + I

With these adjustments, Sumatra PDF becomes a capable night reader while still honoring its lightweight ethos. Whenever you need a bulletproof inversion, let the dedicated PDF tool handle the heavy lifting and keep Sumatra for lightning-fast viewing.