There isn't much of a market, considering so much is available for free and is of high quality (whereas the quality of your work is totally unknown).
You could write a book and submit it to an existing publisher, I suppose. That's selling documents.
You could write a book and submit it to an existing publisher, I suppose. That's selling documents.
You might also want to consider submitting your content to digitalocean or linode, they have great tutorial site.
For self publishing you might want to try Leanpub (https://leanpub.com/)
I also see some great content hosted on gumroad (https://gumroad.com/)