I'm not sure why you'd want to.
Keeping a family from seeing their loved ones' wedding video?
Am I the only one that thinks that's wrong?
I thought that wedding photographers made most of their money through referrals.
From a business point of view I would think that a bad way to build a customer relationship. IMHO.
But regarding your question of encryption, I think that it would be a waste of money to buy that kind of software. However you could just get a pirated copy of the stuff but then you'd be a hippocrite

. Anyway I hope your friend's business does well.