How to convert a PDF to grayscale from command line avoiding to be rasterized?

Question

I\'m trying to convert to grayscale this PDF: https://dl.dropboxusercontent.com/u/10351891/page-27.pdf

Ghostscript (v 9.10) with pdfwrite Device fails with a \"Unabl

Answer 1

A bit late in the day, but the top answer doesn't work for me with a different file. The underlying problem appears to be old code in Ghostscript, for which there is a later version that is not enabled by default. More on that here: http://bugs.ghostscript.com/show_bug.cgi?id=694608

The page above also gives a command that works for me:

gs \
  -sDEVICE=pdfwrite \
  -dProcessColorModel=/DeviceGray \
  -dColorConversionStrategy=/Gray \
  -dPDFUseOldCMS=false \
  -o out.pdf \
  -f in.pdf