Convert a PDF to greyscale for black-and-white printing

A print shop charging by the colour page will count any page with a trace of colour on it, and a document can carry that trace in an image, a shading, a transparency group or a logo nested three levels down. So this does not try to rewrite the colour instructions it can find — it draws each page at 150 dpi into an eight-bit grey image and makes that image the page. The result is genuinely, entirely grey. The price is that the text is now part of a picture, and you should read the limits before you upload.

The text stops being text. Every page comes back as a picture, so nothing on it can be selected, searched, copied or read aloud by a screen reader, and links, comments and form fields are gone with it. Keep the colour original — this copy is for printing.

Convert to greyscale

No account. Your upload is deleted after 2 hours, the result after 24 hours.

How it works

  1. Keep a copy of the original. This is the important step. The greyscale file cannot be turned back into a text document, so the colour original is the only copy that stays searchable and accessible.
  2. Upload the file. There is nothing to configure — no quality setting, no page range, no threshold. Every page goes grey, which is the only answer that satisfies a printer counting colour pages.
  3. Check the result, then print from it. Look at the photographs and any pale highlighting: colours that carried meaning may now be the same shade of grey. The result also tells you the file has become pictures, and roughly why it may have grown.

What this tool does not do

  • The text stops being text. Every page comes back as a picture, so nothing on it can be selected, searched, copied or read aloud by a screen reader, and links, comments and form fields are gone with it. Keep the colour original — this copy is for printing.
  • It is not the right tool for a document that has to stay accessible or searchable. If a print shop only needs the colour ink gone, ask them to print your colour file in mono instead; almost every press can, and nothing is lost.
  • Pages are drawn at 150 dpi. That is sharp enough for body text on A4 and not enough for fine line art, small maps or anything printed at A3 and above.
  • The file usually gets bigger. A page of grey pixels carries more data than a page of instructions for drawing letters, even at one channel per pixel — run compress afterwards if it has to go by email.
  • This is greyscale, not black and white. There are 256 levels of grey and nothing is thresholded, so a pale yellow highlight comes out as pale grey rather than disappearing, and coloured text that contrasted well may end up the same tone as its background.
  • There are no options at all, and no per-page choice. If you need only some pages converted, split the document, convert that part, and merge it back.

What happens to your file

The file is uploaded because Greyscale PDF runs on our server rather than in the browser tab. It is kept for at most 2 hours and the result you download for 24 hours, then a scheduled job deletes both — a job has to be able to read the file while it runs, and you have to be able to retry a failed conversion without re-uploading. Neither needs longer.

Nothing about the contents is logged, and no one reads your documents. The retention page lists the same numbers the code enforces, and the privacy policy says who can reach the storage they sit in.

Questions

Why does the text stop being selectable?
Because the page is redrawn as a picture. The alternative — rewriting the colour instructions in the content stream — leaves the text alone but only reaches colours the stream states directly. It misses colour inside images, shadings, transparency groups and nested forms, and produces a document that is almost grey, which is the worst of both answers when someone is charging you by the colour page.
Will this get me the mono print rate?
It removes every trace of colour from the file, which is what an automatic colour-page count looks for. Print shops differ in how they measure, so if the difference is large, send them one converted page and ask them to confirm before you commit the whole run.
Can I keep the text searchable and still lose the colour?
Not with this tool, and that is a deliberate trade rather than a missing feature. The two reliable routes are to print the colour file in mono at the printer, or to keep the colour original for reading and use the greyscale copy only for the press.
Is greyscale the same as black and white?
No. Black and white in the scanning sense means every pixel is either black or white, which is what fax and bitonal scans do. This keeps 256 shades, so photographs still look like photographs and a light grey rule is still a light grey rule.
Why is my file bigger than it was?
A text page is a short set of drawing instructions; a picture of that page is a couple of million pixels. Even compressed losslessly and at one channel, that is usually more data. Compress will bring it down by re-encoding the page images.
Is 150 dpi enough?
For an A4 page of ordinary text and pictures, printed at its own size, yes — 9 pt type still reads cleanly. For engineering drawings, sheet music, small type under 7 pt, or anything enlarged onto A3, it is not, and you would be better printing the colour original in mono.