Grayscale PDF Converter

People often say black and white when they mean grayscale, but the two are different results. A grayscale page has smooth shading; a PDF to black and white conversion leaves only two tones. If your document has a photograph, a chart with shaded areas or a signature in blue ballpoint, gray keeps all of it legible.

The main reasons to convert are consistency and storage. A color document printed on five different office machines comes out in five slightly different colors, and on a monochrome printer the driver decides how each color becomes gray. Converting once fixes those grays in the file, so every print and every screen shows the same thing. Scanned color pages also get smaller, since one gray channel replaces three color channels.

On a screen, a 50% gray is simply half brightness. On paper, ink spreads a little as it soaks in, so halftone dots print larger than planned and midtones come out darker. Printers call this dot gain, and it is stronger on uncoated paper and newsprint than on glossy stock. Adobe Photoshop's long-standing default gray working space for North American prepress is named after it: Dot Gain 20%.

A PDF can store gray either as plain device gray, which each printer interprets on its own terms, or tied to an ICC gray profile that describes the intended output. This converter produces neutral grays without a print-specific profile and has no dot gain setting. For office printers, archives and screens that is what you want; for offset printing, let the print shop's prepress software apply their profile. If the result looks too dark on uncoated paper, a negative Contrast value opens up the shadows a little.