pdfMB

Grayscale PDF

Turn a colour PDF into shades of gray, or pure black and white, ready to print. Text stays text you can search and copy. Your file stays on this device.

  • No uploadYour file stays on this device.
  • Your original stays as it isYou download a new copy. Your file is never changed.
  • Free, no sign-upNo account and no daily limit.

What happens to your file

Everything below happens inside your browser, on your own device. The PDF is never uploaded, so nobody else, including us, can see it.

  1. pdfMB opens the PDF and goes through the drawing instructions of every page, including form fields, comments, patterns and the pages’ hidden layers.
  2. Every instruction that sets a colour is replaced with a shade of gray of the same brightness. The text, fonts and shapes themselves are not touched, so the text stays searchable and Thai is exactly as it was.
  3. Gradients are recalculated as gray gradients. Spot colours and colour tables are converted to gray in place.
  4. Pictures are converted pixel by pixel. JPEG photos are saved again as gray JPEGs at a quality close to the original. Other pictures are saved without loss.
  5. In black and white mode, everything darker than the level you choose becomes black and everything lighter becomes white.
  6. The new file is saved, and pdfMB draws the pages again on your device to check that no colour is left.
In short
  1. Choose a PDF
  2. Pick grayscale or black and white
  3. Press “Convert”
  4. Download the gray PDF

How to convert a PDF to grayscale

  1. Choose a PDF or drop it on the box. pdfMB shows page 1 as it will look.
  2. Keep “Grayscale” for documents with photos or charts. Choose “Black and white only” for text documents, and move the darkness slider until the preview looks right.
  3. Press “Convert”. A bar shows how far it has got.
  4. pdfMB checks every page for any colour that is left, then you can download the file.

When people use it

Printing at home or at work

Print in gray even when the printer’s colour settings are hard to find, and stop using colour ink by accident.

Saving ink and toner

Black and white only turns light backgrounds, highlights and tinted boxes white, so the printer uses much less ink.

Submitting documents

Some offices and online forms ask for black and white scans or PDFs.

Checking contrast

See whether charts and colour-coded text can still be read when printed in gray or by people who see colours differently.

What it can’t do

  • JPEG 2000 pictures can’t be decoded in the browser, so they keep their colour. pdfMB tells you which pages still show colour.
  • Colours that differ only in hue, such as a red and a green of the same brightness, become the same gray. Charts that rely on colour alone may be harder to read.
  • In black and white only mode, photos lose their shades and light colours disappear. Use grayscale for photos.
  • A digital signature in the file stops being valid, because the file changes.
  • Password-protected PDFs must be unlocked first.

Questions about grayscale PDFs

Is my PDF uploaded?

No. The conversion runs inside your browser, and the file never leaves your device.

Can I still search and copy the text?

Yes. pdfMB changes only the colours. It doesn’t turn pages into pictures, so the text stays text, including Thai.

Will the file get bigger?

Usually it gets smaller, because gray pictures need less data than colour ones. pdfMB shows the size before and after.

What is the difference between grayscale and black and white?

Grayscale keeps every shade from white to black, so photos still look like photos. Black and white only has two colours, which is clearer for text and uses the least ink.

How do I know no colour is left?

After saving, pdfMB draws the pages again (the first 50 in very long files) and looks for coloured pixels. If any are left, it tells you on which pages.

Is there a page or size limit?

There is no fixed limit. Big files with many photos take longer, and very large files can run out of memory on some phones.