Can I upgrade old documents if I upgraded Mediator or MindView?

Yes, your old projects can be updated, but with some limitations: usually a project can only be transferred over one generation.

For example, MindView 4 can open MindView 3 projects; MindView 3 can open OpenMind 2-projects; Mediator 9 can open projects from v8 and v7. Conversion from Mediator 6 to Mediator 9 is not possible, however.