PDF to Grayscale / Black & White

Grayscale, keep text and links. A full-page layer with the PDF "Saturation" blend mode and a grey fill is drawn over each page. Wherever a viewer implements PDF transparency, which all current ones do, that removes the colour from everything below it, so text stays text, links and forms keep working, and the page layout is untouched. The original colours remain stored in the file: it is an appearance change, the file does not get smaller, and a printing pipeline that ignores transparency could still print colour. Check by printing one page.

Grayscale pixels. Each page is drawn at 150, 200 or 300 dpi, converted to grey with the usual luminance weights and saved back as a JPEG (smaller) or PNG (lossless) picture sized to the original page. The colours are really gone, but text is no longer selectable or searchable, and links and form fields are lost.

Black and white pixels. The same rebuild, but each pixel becomes black or white. An automatic (Otsu) threshold suits clean scans, an adaptive threshold copes with uneven lighting, and a fixed level lets you decide. The pages are stored as 1-bit images, which are small. Light grey text, thin lines, photos and shading can disappear or turn into blotches, so this is for text pages.

Grayscale versus black and white. Grayscale keeps shades of grey; black and white keeps two tones only. Neither promises a particular amount of ink or toner saved: that depends on the printer, its settings and the content.

PDF files up to 80 MB. The grey-appearance mode works for any page count up to 500. The pixel modes redraw every page as an image and are limited to 120 pages in the browser. Password-protected PDFs must be unlocked first.

1. Choose a PDF.
2. Pick a mode. Use "keep text and links" when you still need selectable text; use the pixel modes for true grey or two-tone pages.
3. For pixel modes choose the resolution and, for black and white, the threshold method.
4. Press Convert, check the thumbnails, and download.

• Printing a colour PDF on a black-and-white printer and seeing the shades first
• Preparing a scan for an archive or a form that asks for black and white
• Making a text-only black-and-white copy of a scanned document
• Checking how a colour document reads in grey (for example charts and highlights)
• Producing a monochrome copy for a photocopier or fax-style system

The grey-appearance mode changes how the file looks, not what it contains: colour data stays in the file, the file does not shrink, and a viewer or printer that ignores transparency can still show colour. The pixel modes keep the page layout but turn the page into a picture: text is no longer selectable, links, form fields, bookmarks and tagging are lost, and file size can grow or shrink depending on the page.

Black and white cannot represent light grey, so pale text, thin lines, shading and photographs may disappear or become noisy; check every page. No percentage of ink saving is promised. Large pages at 300 dpi use a lot of memory and can be slow.