Database Workbench Pro includes a set of Diagramming Tools allowing you to do the following:
•Create an abstract Conceptual Data Model (CDM) (sometimes called an Entity-Relationship Diagram)
•Generate a database system specific Physical Data Model (PDM) from a CDM
•Create a database system specific Physical Data Model and generate a SQL Script to create this database
•Reverse engineer an existing database into a Physical Data Model
•Visualize relationships between tables in existing databases
When editing a diagram, you can use "Notes", "Groups" and more tools to enhance your diagram and it's usability.
Diagram Editor Example