On a profile page, there is a greyed-out button that says download archive of my posts.
Obviously it’s not been implemented, but I’m sure it will be a neat feature once it is.
Here’s a feature suggestion along the same lines:
Have an option for the admin to enable a button for a post that says download PDF of this post. (or epub or .odt or txt file, etc)
This could come in handy if an admin wants to use Discourse to post lengthy tutorials.