How to clean up a grey or speckled scanned document

Which defect am I trying to remove?

Identify the problem before moving every control. Grey paper needs a different treatment from isolated dark speckles, and soft text is different from a page photographed out of focus. Keep the original available at the same zoom for comparison.

Use Enhance PDF for a scanned PDF or its supported image workflow for a single picture. Work on a copy. If the page is clipped or genuinely unreadable, the scan preparation guide explains when a fresh capture is more useful than stronger cleanup.

What does contrast change?

Contrast increases the separation between light and dark areas. A modest adjustment can make writing stand out from grey paper. Pushing it too far can turn a faint pencil note into the same light value as the background or fill in the gaps inside small letters.

Pick one page with the weakest writing. Compare that writing after each adjustment. A strong printed heading is a poor test because it can stay readable while more delicate information disappears.

When do denoise and sharpening help?

Denoise targets small unwanted variations such as speckles. It can also soften tiny punctuation, so check decimal points and dots over letters. Sharpening increases local edge contrast. It may make a modestly soft stroke clearer, but excessive sharpening can produce halos and emphasise noise.

Do not use sharpening as proof that an ambiguous digit has become correct. If a 3 and an 8 were indistinguishable in the original capture, a more pronounced edge can still represent the wrong shape.

What did our upscaling test actually do?

We ran KovaPDF's image enhancement with a 2× upscale, grayscale and a modest contrast adjustment on a 1240 by 1754 pixel sample. The output measured 2480 by 3508 pixels. Both dimensions doubled, giving roughly four times the pixel area.

That is a processing measurement, not recovered information. In a separate PDF run, enhancement alone still produced no selectable text from this image-only sample. For searchable words, use OCR PDF after checking the cleaned picture.

Should I use a black and white threshold?

A threshold assigns pixels to dark or light rather than keeping intermediate shades. It can produce a clean page from evenly lit black print. It can also remove light handwriting, merge closely spaced strokes and destroy distinctions between coloured marks.

Compare a thresholded result with grayscale before choosing. Inspect a stamp, a thin rule, a decimal amount and any correction. If the background remains slightly grey but every mark survives, that can be the better document.

What order should I use for the rest of the job?

Clean first, review the picture, then recognise text if needed. Proofread important values after OCR. If you intend to change the recognised words, follow editing text in a scanned PDF, because recognising a word is not the same operation as removing its original printed pixels.

Reduce file size only after the content is settled, and inspect the compressed copy again. A smaller output can come from a changed image representation, but a small file is not evidence that the cleanup preserved every meaningful mark.