How to brighten a PDF and whiten a scan

Job 1: the whole page is too dark

Underexposed phone photos of documents and heavy photocopies have mid-tones that sit too low. Raising brightness lifts them. The control to look for is one that never moves pure black or pure white, so the ink does not wash out and the paper does not clip. That is how the Brighten PDF tool works.

Job 2: the paper is grey or cream

A scan records the colour of the paper. The fix is background whitening, which moves paper-coloured pixels to white. A good whitening step leaves darker pixels alone: Whiten PDF background does not touch anything darker than about 55% of the paper brightness, and it removes the colour cast so cream paper becomes neutral white rather than a lighter cream.

Job 3: one side is darker than the other

That is uneven lighting, from a phone held over the page or a book spine curving away from the glass. Neither brightness nor whitening fixes it, because a shadow is a local problem and both controls are global. Remove scan shadows estimates the paper level across the page and brightens each region to match.

The trap: brightening faint text

If the real problem is that the text is faint, brightening makes it worse. Brightness lifts the ink as well as the paper. Measured on this site’s faded demo scan, a Standard brighten moved the ink from 187 to 217 and the paper from 231 to 255, so the gap between them went from 44 down to 38. The page looked cleaner and read worse. For faint text use contrast or Fix a faded PDF.

Steps

1. Decide which of the three jobs you have. If you are not sure, zoom in: dull everywhere is Job 1 or 2, darker on one side is Job 3, faint text is not a brightness problem.
2. Use the matching tool and pick the lightest setting that works.
3. Drag the before/after slider and look at the smallest text and at anything pale.
4. Raise the strength only if needed. Strong settings can wash out light pencil and shading.
5. Download the new PDF. The original is never modified.