Depends if you want anyone in the world to be able to find it with a Google search, or just sharing with a friend.
If it is just for a friend you can use things like Google Docs (if a .pdf, Word doc, pictures or other) or upload to a private post on Imgur (if it is pictures like .jpg).
As for a search for anyone via Google, I am not sure.
If it is something spectacular or very rare, you might even try Forgotten Weapons: although more famous for his videos, Ian's original intent was this very thing (putting rare manuals and documents online for everyone).