How do you remove the documentation installed by gem install?

Gem documentation is installed in [RUBY]/lib/ruby/gems/doc, where [RUBY] is the directory into which you installed Ruby (C:/ruby on my machine).

I don't see why you shouldn't just delete the folders representing the gems for which don't don't need documentation: you can always regenerate it.

run this command:

rm -r "$(gem env gemdir)"/doc/*

on windows if you use cygwin