There are website that leave you use their etherpad instances for free, some of them also contain other similar tools like ethercalc, etherdraw, …
And if the default seems you not much, there is a lot of plugins that you can add to your personal instance.
Pros
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not user account needed
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rich text format
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history of modifications saved
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Can be installed anywhere
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chat with other users
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export document to multiple formats (html, pdf, …)