Yes, just copy the entities back to the feature service layer. However, this ONLY works if you are adding new features.
If you want to allow someone to modify feature service feature classes (even outside your organization and disconnected to your network),as long as they are using ArcGIS for AutoCAD to make the edits they can leave them as FEATURE SERVICE layers in the drawing and whenever you get the drawing back you can SYNCHRONIZE.
- Feature Services DO work completely disconnected.
- When adding to new features as long as the schema's match you can move entities in a local feature class to onto an AutoCAD layer of the feature service and that will add the attributed feature to the feature service when you synchronize.
-Don