Password for verify distribution of ibooks document

There are a possibilitie to protect the main document with a password but as soon as you export that document so the customer can verify (download to an iPad) then the password is gone.

Security risk since I only whants to share the almost done document with the trusted person and don't want to lose all work just before I'm done.

Export to pdf is not a solution since then all movies etc. is gone.

Any suggestion?

Regards,

Claes