4.5b to 6.7 is a pretty big step. As far as I know, you need to go at least to 5.1c. This is basically a separate installation with a migration of data as the architecture of the whole system was changed.
is the system requirements for version 5.1c.
I would not recommend to do this change by yourself, please involve you DocuWare partner and maybe even DocuWare support. They can also provide you with the needed versions.
Then you need to upgrade to 6.7, the system requirements are here