I've been using SignNow.com to have clients electronically sign documents. I frequently need signatures for agreements and acceptance forms, and SignNow.com gives me a free, simple, legal way to get them. These are the general steps:
Either party can also add text notes. I ask clients to enter dates this way. For signatures, you can use plain text, have SignNow generate a stylized signature (this is legal), or upload your own signature (I did this).
Learn more at SignNow.com. What do you use for electronic document signing?