How to convert a PDF to grayscale (black & white) in your browser
Turn a colour PDF black and white to save ink on mono printers and faxing, entirely in your browser with no upload — and know the one trade-off (text becomes part of the page image) before you start.
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Grayscale converts every page of a colour PDF to black & white right in your browser — the file is never uploaded to a server, so nothing about it leaves your device.
Before you start
- Grayscale is free and doesn't need an account.
- Everything runs locally. Unlike most online converters, AttachKit never uploads your PDF — you can open your browser's DevTools network tab and watch.
- If the PDF is password-protected (it asks for a password to open), remove the password first with Unlock. The tool can't open an encrypted file and will point you there.
- Know the one trade-off: a PDF's colours can't be honestly changed in place in the browser, so each page is re-rendered as a grayscale image. That makes the output print-ready, but the text is no longer selectable or searchable — like a scan. Searchable (OCR) can restore a text layer afterwards.
- There are no modes or settings to choose — every page is converted, in one click.
Steps
- Open Grayscale.
- Drop your PDF onto the drop zone, or click it to pick a file.
- Click Convert to grayscale. The button shows "Converting…" while pages are rendered one at a time on your device — a long document can take a little while.
- Read the result card: it confirms how many pages were converted, e.g. "12 pages converted to grayscale". Below it, an amber notice reminds you that pages were re-rendered as grayscale images and links to Searchable (OCR) if you need selectable text back.
- Click Download grayscale PDF. The file saves as
yourfile-grayscale.pdf— your original is untouched. - Click Convert another to start over with a new file, or use the "Fill it →" action on the download toast to open the converted file straight in Fill for filling and signing.
What the conversion actually does:
| Aspect | What happens |
|---|---|
| Colour | Each page is rendered, then desaturated to grayscale. |
| Resolution | Pages are rendered at roughly 144 DPI, with the longest edge capped at 2600 px so huge pages can't blow past browser canvas limits. |
| Page size | The output page keeps the original page dimensions, so paper size and layout are unchanged for printing. |
| Rotation | Pages that carry a rotation flag are baked upright, so they print the way they display. |
| Text | Becomes part of the page image — no longer selectable or searchable until you run OCR. |
Result
You get a black & white copy of your PDF named yourfile-grayscale.pdf, created entirely on your device — ideal for mono printers and faxing, and it saves colour ink even on colour printers. Every page is converted; there's no partial or per-page option. If you need the text to be selectable or searchable again, run the result through Searchable (OCR) — the result screen links there directly.
One honest note: because pages become images, a text-heavy PDF can come out larger than the original. That's expected — see the troubleshooting guide for what to do about it.
Related
- Grayscale troubleshooting — password errors, lost text, bigger files, colour that won't go away
- Unlock — remove a password so the PDF can be converted
- Searchable (OCR) — restore selectable, searchable text after converting
Related
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