Vellum takes the colour out of a PDF document by computing the perceived luminance of every pixel, the method that preserves the original contrasts — a green logo and a blue background do not end up as the same grey. Three resolutions are offered, from 150 dpi for on-screen reading to 300 dpi for professional printing, with a before/after preview of the first page. The document produced is made of images: its text can no longer be selected, and optical character recognition is what makes it searchable again. The conversion is computed by your browser, without the file being sent to a server.
It computes the perceived luminance of every pixel, a method that preserves the original contrasts — a green logo and a blue background do not end up as the same shade of grey. Three resolutions are offered, from 150 dpi for on-screen reading to 300 dpi for professional printing.
No, the conversion produces a document made of images: the text is no longer selectable, and optical character recognition (OCR) is needed to make it searchable again. That is the trade-off of this method, which faithfully preserves the contrasts.
150 dpi suits on-screen reading, 300 dpi suits professional printing at the cost of a larger file. The tool is free, and the calculation happens in your browser, without the document being sent to a server.
Vellum — free PDF tools whose processing stays on your device.