Can user who is not employee of supplier process supplier's doc in SUS?

Dear,

As you know, only user for employee of supplier can process documents of their own in SUS. My client raise a question that how can their IT provide support if the supplier encounters a problem while processing invoice in SUS. Mean...any possible for internal admin user who is not employee of the supplier to view and process the documents of the supplier?

Thank you in advance for your time.

Best Regards,

Bob