Can Adobe Interactive PDF consume a service that returns JSON? A few web sites seem to suggest it can:
Its probably better to post this in the Form or Designer forum as those ones deal more with the capabilities of XFA based PDFs. The Generator forum deals with the server software that converts documents to PDF.
Having said that.
You should be able to do it, but not directly. I don't believe that there is a way to map the JSON returned values to a field, as XFA pdf's generally support XML. You may be able to put the returned JSON value into a single field and then write some code that would parse that value into the proper fields.