I've run into a similar issue. The problem i'm having is that user preferences is a collection. The individual user preferences do not have an ID which means you can edit them individually and the userPrefValues collection is very large so you can't edit the collection via an API call.

How can I use Workfront Fusion to turn on AutoProofGeneration either for a document and/or a user?

I am trying to have an automated iterative process for reviewing content: 1. A file is uploaded to a issue and then via WF Fusion, a proof is created.(Working)2. A new version of the file is uploaded, then via WF Fusion, a new version of the proof is created and linked to the new doc version in the ...