ebooks: finding a distrubution avenue to provide free copies to select customers

We would like to find a distributor to distribute our ebooks that allows us to sell the book, but still allows us to provide the book to some clients at no cost as marketing tools or as a gift. Any help in the matter would be great.

I had once purchased a “book” online that I needed a password to access and I was only able to open it on the computer I originally downloaded it to…. if anyone has any ideas on the software used to create this situation I’d be interested in knowing that too.

Thanks in advance for any help with either of these.