Convert a PDF to black and white

How to convert a PDF to black and white

1. Pick a black level above. Standard is selected to begin with.
2. Choose your PDF, or drop it on the page. It is processed in your browser and never uploaded.
3. Drag the slider to compare the original with the black and white version. Zoom in on small text and on anything faint.
4. If light text has gone, choose Light ink. If grey paper has filled in with black, choose Dark scan, or raise Whiten paper first. Then press Apply new settings.
5. Download the new PDF. The original is left untouched.

Black and white versus grayscale

The two are easy to mix up.

• Black & white is a threshold. Each pixel is judged by its lightness and becomes pure black or pure white. There are no greys.
• **Grayscale** keeps all the shades of grey. It is the safer conversion for anything with shading, photographs, stamps or signatures.
• Because black and white throws away every mid-tone, it cannot be undone. Keep the original.

How the threshold works here

The page is first corrected for uneven lighting, so a shadow does not turn into a block of black. Then the Black level sets where the cut-off falls: a higher level turns lighter ink black, and a lower level stops grey paper and shading from filling in.

• Black level moves the cut-off between black and white.
• Whiten paper first pushes grey paper towards white before the cut-off, so it does not cross to black.
• Speckle removal clears isolated dust specks so they do not become hard black dots.

When black and white is a good choice

• Plain text documents, forms and typed pages on clean paper.
• Faxes and line drawings.
• Scans you want to look crisp when printed on a laser printer.
• Pages where you want strictly two tones, for example before further processing.
• Smaller files. A two-tone page compresses very well: the demo sample went from 86 KB to 24 KB. How much you save depends on the document.

When it is not

• Photographs and anything with shading, which turn into blotches.
• Signatures and stamps, whose thin or pale strokes can break up or vanish.
• Faint pencil and light highlighter, which sit near the paper level.
• Colour-coded content, because all colour is reduced to black or white by lightness.
• For these, use grayscale instead.

Digital pages and scanned pages

• Pages made of text and vector graphics have their colours set to pure black or white, so the text stays real, selectable text.
• Pages that contain images, including every scan, are rendered at 200 DPI, thresholded, and written back as black and white images. Their text becomes part of the image.