How can I generate a monochrome pdf file from a color pdf file?

I have tried ImageMagick's convert, but with bad results.

A direct conversion

convert -monochrome file.pdf file-bw.pdf

produces dithered images.

Going through png

convert -monochrome -background white -geometry 2048 file.pdf file-bw.png

stubbornly keeps the background to some shade of gray.

2 Answers 2


You can do this easily in Preview:

  1. Open the PDF in Preview.
  2. Go to File > Export...
  3. From the Quartz Filter drop-down box, select Black & White.
  4. Save and you're done.

You can also use Ghostscript to transform color into grayscale PDFs. The most recent version is v. 9.05, which is the recommended one for this task.


 gs \
   -o grayscale.pdf \
   -sDEVICE=pdfwrite \
   -dPDFSETTINGS=/prepress \
   -sColorConversionStrategy=Gray \
   -sColorConversionStrategyForImages=Gray \
   -sProcessColorModel=DeviceGray \
   -dCompatibilityLevel=1.4 \

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