Sell it as a $40 book on Amazon

Share a link to wherever it's hosted. I like that notes almost always have links instead of attachments..

upload to google drive and link to nostr. if the link goes down you can post a new one in reply to the original note. nostr is a transport protocol not a storage one

Not at all. Nostr is not for hosting files.

You don't really "host on nostr".

If you have a large pdf you need to share, you can host it on a static site and reference it here.

The easiest way is to just share a downloadable link.

Google drive

Dropbox

Github pages

If censorship is a issue:

Onionshare or torrent