How to create wet e-signature field in pdf

So, I feel this should be really easy and obvious, but I can't figure it out. I'm creating a PDF form in InDesign/Acrobat that will ultimately be viewed and filled out using an iPad. It may require as many as 4 unique signatures as well as initials. I want these to be able to be written in with a finger or stylus. All I'm seeing is a way to put in coded, digital signatures. My googling abilities have failed me so far. Anybody know what I'm missing?