Router inside router…

Have router1 inside another router2 controlled network. Router1 has PCs needing access to shares available in router2 network. How to make this happen?! At present a static IP printer on router2 network is accessible to both networks, but a data server in router2 network can only be seen by router2 network. Both networks use NAT but use addresses that do not conflict (router2 addresses are limited to .100-.107 and router1 addresses are limited to .111-.112 to prevent overlap.

Ideas?