Unexpected API error response on createPersonalUrlWidget() request

Hello - I'm working out a way to have our customers sign an agreement placed in an iframe on our site. The customer will be logged in, and I've created a widget template to be used in the admin. When I try to generate a createPersonalUrlWidget to provide a url to embed in an iframe, I get the following response from the API (v20):

One or more errors has occurred.  Document Title is required.

There is no reference to where this is being triggered, I would assume that it would be in the fileInfos portion of the requeset, but according to the documentation, I'm passing all of the required parameters into the request already. Where do I add the 'Document Title'?