I've got a free account on box.com and I email a link so they can download from the cloud. This is nice because I don't have to worry about attachment size, or having to resend it if they accidentally lose or delete it, or it gets corrupted. Each document is customized, so resale isn't really a concern of mine. Downloading from the cloud also means I don't have to worry about getting additional contact info, so I can just send an Etsy message with the link, which gets the dialogue going between us, and this has already led to additional sales and custom item requests for me! [Not many yet, since I'm just starting, but it's still exciting!]