Change the colours used in a PDF, or invert them entirely. Inverting turns a black-on-white document into light text on a dark background, which is easier on the eyes when reading for long stretches on a screen and uses noticeably less power on an OLED display. Higher contrast colour choices also help with low-vision reading.
Generally no - an inverted document prints as a solid dark page and consumes enormous amounts of ink. This is for reading on screen. Use Adjust PDF Contrast if the goal is a cleaner print.
Inverting affects everything on the page, so photographs come out as negatives. Documents that are mostly text handle inversion far better than illustrated ones.
The effect is similar, but this writes the change into the file so it looks the same everywhere, rather than depending on a viewer setting.
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