Brad, I went through the same thing on updating images. Instead of reading the documentation (pdf files), did you check out the video tutorials under 'Archived Documentation'? The video give you a good visual how it is done step by step. If you created your pages using Data Assist and then go into the update page to the form field where your image upload is, you click once on that form field on go to your 'Quick Tag" editor or directly to the code and change the input type from "text" to "hidden". Right next to hidden form element (let's call it 'img'), go to forms in DW and add a new form element called 'file' field. In the properties, name that File Form element 'imgFile' and press ok/done. You will then add WA Digital File Pro 'Upload file' behavior. The trigger should be set to the 'Update Button pressed', and not 'any form post'. In the file field, it should already be set to 'imgFile'. In the 'Default File' field, click on the lightning bolt and open up the WADA UpdateForm folder and select the 'hidden' form element named 'img'. Once that is complete, you need to change the 'Update Record' in the server behaviors panel. When the panel opens up, continue to the next step leaving the settings as is. On the second step, click on the 'WA File Upload (img)' to open up and select 'Server File Name' from the list. Click finish and that should do it.
Again, go to the following links to the video tutorials and it explains this very thoroughly. It works, believe me. There are two parts to this video tutorial:
I hope this helps.