How to convert a PDF to black and white for cheaper printing

Why this saves money

Printers and copy shops charge by page, at different rates for colour and monochrome. The catch is how a page gets classified: many printers count a page as colour if it contains any colour at all, including a faint logo in the header or a coloured hyperlink you forgot was blue.

A 60-page report with a blue heading on every page can be billed as 60 colour pages. Converting to grayscale first removes the ambiguity — there is no colour left to detect, so every page bills at the monochrome rate.

This is the single most common way people overpay at a print shop, and it is entirely avoidable in one step.

Converting the file

Everything else is left alone. Page size, layout and text positioning are unchanged, so the document paginates exactly as it did before.

1. 1Open the Grayscale PDF tool and choose your document.
2. 2Convert — colour images become grayscale and coloured text becomes black.
3. 3Check the preview, particularly any charts, then download.

The other benefit: smaller files

A colour image stores three values per pixel — red, green and blue. Grayscale stores one. Removing two-thirds of the colour data makes a real difference to file size, particularly in scanned documents where every page is an image.

This is why grayscale conversion pairs so well with compression. Convert first, then compress: you are compressing a third of the data, and the result is usually much smaller than compressing the colour version.

It often makes scans look better

This surprises people. Scanners and phone cameras give white paper a faint colour cast — yellowish under indoor lighting, bluish in shade — and it varies from page to page as the light changes.

The result is a document where every page is a slightly different shade of not-quite-white. Converting to grayscale removes the cast entirely and makes the whole document consistent, which reads as more professional even though no detail was added.

When not to convert

Anywhere colour carries meaning rather than decoration, converting destroys information — and it is not recoverable afterwards.

The clearest case is a chart with a colour-coded legend. Three lines in red, green and blue become three lines in nearly identical greys, and the legend becomes useless. The same applies to colour-coded maps, heat maps, wiring diagrams, and any document where a status is indicated by colour alone.

Also think twice about branded material going to a client, photographs where colour is the point, and anything being submitted where the recipient specified colour.

If a chart matters and the document must be monochrome, change the chart at the source to use different line styles or patterns rather than colours. That is the accessible choice anyway — colour-blind readers face the same problem your grayscale printer does.

Grayscale, not pure black and white

Worth being precise about the terms, because they are used interchangeably and mean different things. Grayscale keeps the full range of greys, so a photograph still looks like a photograph.

True black and white — every pixel either fully black or fully white — is a different conversion, and it destroys photographs while making text scans very small and very crisp. If a scanner offers a black and white mode, that is what it means.

For general documents, grayscale is what you want. It is what this tool produces, and it prints at the monochrome rate exactly the same way.

Printing economically, in order

A 100-page colour document printed single-sided costs a small fortune. The same document in grayscale, 2-up and double-sided is 25 sheets at the cheap rate — and still perfectly readable for anything you are not submitting formally.

1. 1Remove the pages nobody needs — appendices, blank backs, duplicate covers.
2. 2Convert to grayscale so every page bills at the monochrome rate.
3. 3Use N-up to print two or four pages per sheet for reference material.
4. 4Print double-sided, which halves the paper again.
5. 5Compress last if you are also emailing the file.