Turn Paper Scans Into Clean PDFs

What makes a photo look like a scan

A phone photo of a document and a flatbed scan differ in three specific ways. The photo includes the desk or table around the page. Its lighting falls off toward the edges, so one corner is darker than the other. And its whites are grey rather than white, because a camera exposes for the whole scene rather than for paper.

The scan tools here address all three: trimming the border, lifting contrast so text separates cleanly from the paper, and normalising the tone so the page reads as white. The result is an image-based PDF that portals asking for “a scanned copy” will accept.

Photographing a document properly

Processing can correct a mediocre photo but not rescue a bad one. Lay the page flat, shoot straight down rather than at an angle, and fill the frame with the page. Use even light with no shadow falling across the paper, and avoid direct overhead light that produces glare on glossy stock.

Auto crop works by trimming an even-toned border, so it needs the surface behind the page to differ clearly from the paper. A white document on a white desk gives it nothing to find. A dark table is ideal.

Choosing colour, grayscale or black and white

Black and white forces every pixel to one extreme. It gives the crispest text and by far the smallest files, which makes it the right choice for a text-only document heading to an upload form with a size cap. Grayscale keeps the full tonal range and suits documents containing photographs or shaded diagrams. Colour is only worth its file size when the colour carries meaning — a coloured stamp, a highlighted clause, a colour-coded form.

Getting a scan under a size limit

Scanned PDFs are photographs, which is why they are large and also why they compress so well. If a portal caps uploads at 100 KB or 200 KB, convert in black and white first and then compress — starting smaller always beats squeezing a large colour file afterwards. Each processing pass discards detail that cannot be recovered, so doing it once at the right settings gives a visibly better result than doing it twice.