Grayscale PDF
Convert a PDF to grayscale so it prints without colour ink, or meets a rule that documents must be black and white.
How the files you choose are handled is set out in the privacy policy.
How to convert a PDF to grayscale
- Tap Choose a PDF.
- Choose a sharpness. Good suits reading and everyday printing.
- Press Convert to grayscale, then Save PDF.
Why make a PDF black and white
- Printing costs. Print shops and office printers charge several times more for a colour page than a black one, and a single blue link or logo can make a page count as colour.
- Submission rules. Courts, patent offices, some journals and exam boards require black and white documents.
- Seeing what a mono printer will do. Colours that look distinct on screen can turn into the same grey on paper. Converting first shows you whether a chart still reads.
- A calmer look. Scans of yellowed or tinted paper look cleaner without the colour cast.
Grayscale is not the same as pure black and white
| Kind | What each dot can be | Looks like |
|---|---|---|
| Colour | Any colour | The original |
| Grayscale | Black, white or any of about 250 greys between | A black and white photograph |
| Pure black and white | Only black or only white | A fax or a photocopy |
This tool makes grayscale. Photographs keep their shading and coloured text becomes a matching grey. It is what people nearly always mean by a black and white PDF, and it is what a printer set to “black only” produces.
How colours turn into greys
Each colour is replaced by a grey of the same lightness. Yellow, a light colour, becomes a pale grey. Dark blue becomes a dark grey. Two different colours of similar lightness, such as a mid red and a mid green, come out as almost the same grey. If a chart depends on telling those apart, give its lines different styles or labels before converting.
Light yellow highlighter on white all but vanishes, and pale coloured text can become hard to read. Check those pages after converting.
Pages become pictures
To guarantee that no colour survives anywhere, whether in text, drawings or embedded photos, each page is redrawn as a grey picture and the PDF is rebuilt from those pictures. Two consequences follow.
- Text can no longer be selected or searched, and links and form fields are gone. Keep the original for those.
- Sharpness is fixed at the setting you choose. 150 dpi is comfortable on screen and fine for normal printing. Choose 200 dpi for small type or detailed drawings. The page size in the document is unchanged.
File size can go either way: a document of scanned colour photographs gets smaller, while a text-only PDF gets larger because pictures of text weigh more than text.
Related tools
To reduce the size afterwards, or instead, use compress PDF. To get individual pages as pictures, use PDF to JPG. Password-protected PDFs can be converted if you know the password.
Questions
How do I convert a colour PDF to black and white?
Choose the PDF and press Convert to grayscale. Every page is redrawn in shades of grey.
Will it save printer ink?
It guarantees no colour ink is needed. Whether less black is used depends on the document.
Can I still select the text afterwards?
No. Pages become pictures so that every trace of colour is removed. Keep your original for searching and copying.
Is this true black and white, like a fax?
No. It is grayscale, with shades of grey, which keeps photographs and shading readable.
Why did my file get bigger?
A page of text stored as a picture takes more space than the text did. Choose a lower sharpness, or compress the result.