There are a couple of products that can do this.
There is a simple java app from OT that can build the user list from an excel spread sheet, but it does not set all the user features.
There is also a product from Global Cents, called Power Tools for Deployments, that allows you to do migrations of data from 1 Livelink instance to another. You go to the source instance and select the users/groups that you want to create in the new instance, export them, move the export to the new instance, then import them. The product creates the users and groups and populates the groups so that they have the same membership as the source machine. The user notification settings are also copied to the new instance.
That same product also migrates objects from 1 instance to another maintaining all the permissions, metadata, and links between the objects.