Hi Alex,
I'm also new to Ariba and haven't gotten to SPM yet in our implementation. My understanding is that you would run one SPM for the supplier and it would have an occurrence, say every 6 months or once a year.
The SPM should have a document tab where you can place documents. If you create many SPM for a supplier and have information in other areas as well then maybe you can work with the Supplier Workspace. The supplier workspace has a 360 Report. Maybe you can get the consolidated overview there?
I'm curious to know what you end up with.
Br
Chr