Can I make my publications completely private?

Can you clarify this issue for me?

I think that when Issuu uses the word "private" for documents it means: not offered up to be indexed by Issuu or the search engines. However, private documents are accessible by anyone on the internet via the URL.

I ask this because I currently have a password-protected site which I use as an extranet to distribute privileged content to my clients who pay for it.

Is it the case that there is no way for me to use Issuu to distribute content to my users currently with it being password-protected, or protected with long URLs?

This is also on my wishlist, to make a publication completely private would be a huge feature for me.