Thanks again Charles. But no, the API examples don't include an example for assigning workflow programmatically. They all assume the document already has a workflow. If anyone happens to know the answer I'd be interested. However...
...thanks Rui, I had actually come to the same conclusion. I think you're right that Advanced Workflow is the way to go for this purpose.
(@Charles - no, I simply hadn't considered that option - relatively new to Kentico!)