How to convert PDF to Grayscale

I found a solution in a blog post:

With GhostScript (and Windows users can access gs via cygwin), you can do it with the following command:

gs \
  -o grayscale.pdf \
  -sDEVICE=pdfwrite \
  -sColorConversionStrategy=Gray \
  -dProcessColorModel=/DeviceGray \
  -dCompatibilityLevel=1.4 \
   source.pdf

This will convert source.pdf to grayscale.pdf and not put you into a GhostScript shell (due to the -o option instead of the -sOutputFile= option).

Sounds like a job for Imagemagick. Windows and Linux versions are available.

http://www.imagemagick.org/script/index.php

This should do the trick at the command line:

convert -colorspace GRAY original.pdf grayscale.pdf