Black and White PDF

How to make a PDF black and white or grayscale

1. Choose the PDF (or drop it on the box).
2. Choose Grayscale (every colour as its shade of grey) or Black and white (crisp, for forms that ask for it, and smaller). For black and white you can make it lighter or darker.
3. Tap Make it; the pages show as they came out. Download or share the PDF.

Everything happens in your browser: the PDF is never uploaded to ap7am or anywhere else. The new file keeps your PDF's name, such as certificate-grayscale.pdf.

Text stays text

The pages are not turned into pictures. Each colour in the PDF is changed where it is set: the colours of text, lines and filled shapes, in the pages, in drawings used on several pages, in patterns and gradients, and in comments and form fields. So text stays sharp, selectable and searchable, and the file usually gets smaller, not bigger. Grey is worked out the way JPEG and most printers do (Rec. 601 weights: green counts most, blue least), so colours keep their lightness: dark blue stays dark, yellow stays light.

Pictures

• Grayscale: each colour picture is made grey. A photo saved as a JPEG is saved again as a grey JPEG at about its own quality; other pictures are stored without losing anything. A picture with few colours keeps its pixels and only its colours become greys.
• Black and white: each picture becomes true black and white (one bit a pixel, which is why scans get much smaller). The paper is evened out first, so a shadow across a phone photo of a page comes out white, then text is split from the paper at the best level for that picture; photos inside it are kept as fine dots, as in a newspaper, so a face stays a face.

Black and white: what turns black and what turns white

Text and lines become pure black unless they are very light. Dark fills become black and light ones (pale yellow boxes, light grey shading) become white, for a clean background. A mid-tone fill, such as a grey bar behind a heading, keeps its grey, so whatever is written on it stays readable. Lighter and Darker move these limits.

What cannot be changed

A few rare things are left as they are and the page says so: a small picture stored inside the drawing itself, and colours whose definition cannot be read. Pictures that are already black and white stay as they are. A locked PDF opens with its password; its pages then go in as pictures (grey or black and white), which the page says.

Questions

Made with pdf-lib (MIT licence) and Mozilla's pdf.js (Apache 2.0 licence), both running in your browser.