Honestly, one hen is not going to be enough! I am sorry to be so upfront about it but have made the same mistake. Pekin drakes are really active boys. Only adding one hen is a death sentence for her. I have kept pekin almost 4 years now, started with a pair. I did some fast scrambling to get more hens! I won't keep more than 1 drake and I have 6 pekin, several misc. breed ducks for him. My Rouens are not nearly as aggressive a breeder, but those drakes are able to ward off the pekin drake from the rouen ladies. Craigslist may be a good source to find them, or ask your local feed supply if they have a duck breeder in mind.
Yes I've had several people tell me this. I'm planning on getting two females and trading one of my males. That way I will have two pairs. Thanks!