When reading a PDF file at night for a long time, the overwhelming brightness may hurt your eyes, TechEDMentor will solve this annoying problem. The following are the steps to change PDF themes.
1. Click Page Display 
on the toolbar -> find Theme in the right panel;
2. There are 4 different themes for you to choose: Light, Sepia, Dark, and Reseda;
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Light Mode: The default one that displays the document on a bright white background.
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Sepia Mode: Displays the document in a light-yellow background, so it’s easier on your eyes.
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Dark Mode: Displays the document in inverse color (like it is on film negatives) in a dark environment.
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Reseda Mode: Displays the document in a light-green background to protect your eyes after long-time reading.
3. Or you can customize the color according to your preferences, click More -> choose a color or click More -> tap Set Custom Colors -> choose a color and click Add to Custom Color -> click OK -> tap the new theme to change the PDF theme.
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