That is in principle always possible.
First you need to export from the old system your data files (documents) and their corresponding meta data including access control lists.
Secondly you need to import these into the new system.
Most critical issue are the access control lists. Different system handle access rights differently. The mapping from one system to the other system is crucial. Also mind boggling may be the mapping of meta data!
After all: Know your requirements before starting.
Hope that helps
Frank
