Forcing grayscale PDF to Black and White?

I have a large color PDF that I can easily view greyscale in Foxit Reader:

Unfortunately various bits of text end up in ridiculously light shades of grey. Similar, but not direct, questions include:

• Displaying PDF files white on black
• Converting a PDF to black & white with ghostscript
• Convert a colored PDF into a white/black

How can I force a PDF to display only in pure black and white?

2 Answers

ImageMagick is free and cross-platform. This command should work:

convert <input> -threshold xx% <output>

For example:

convert original.pdf -threshold 50% new.pdf

You'll have to set the threshold to taste.

If you want to avoid downloading and working with the command line in ImageMagick, there's an online tool that can create pure Black and White from PDFs:

The B&W Threshold and reverse features may help with light elements.