This is a Bash function I have in my .bashrc. This function uses Ghostscript (gs), which must be installed in the system.


# Convert pdf to grayscale
function pdf2gray {
gs \
-sDEVICE=pdfwrite \
-sProcessColorModel=DeviceGray \
-sColorConversionStrategy=Gray \
-dOverrideICC \
-f $1 \
-o $2
}


In this example a file called abc.pdf is converted to grayscale copy called abc_gray.pdf. The first argument is the input file and the second argument is the output file. Note: My function doesn’t check if these are given or not.


pdf2gray abc.pdf abc_gray.pdf