Convert PDF to Grayscale & Black/White

Why convert to grayscale

Colour printing costs several times more per page than black and white, and most office and home printers will draw from colour cartridges even for a document that only carries a coloured logo. Converting to grayscale first removes that entirely.

It also reduces file size, often substantially. Colour data is roughly three channels of information; grayscale is one. On a scanned document the saving is typically 20-30% on top of any compression.

What changes and what does not

Every page is converted to 8-bit grayscale, so colours become shades of grey chosen by luminance. Page count, page dimensions and the position of everything on the page are unchanged.

One thing worth checking: colours that differ in hue but match in brightness - a mid red and a mid green, for example - converge to nearly the same grey. On a chart that relies on colour to distinguish series, the result can become ambiguous. Charts with patterns or labels convert without issue.

Grayscale or black and white?

Grayscale keeps the full range of tones and suits documents containing photographs. Pure black and white, available in the scan tool, forces every pixel to one extreme and produces the smallest files with the crispest text, but destroys photographs entirely. For a text document destined for a portal upload, black and white is often the better choice.