Schema Visualizer allows you to create fully featured Entity
Relationship Diagrams (ERD) based on any database which could be
accessed with help of Oracle SQL Developer. Tables can be added to an
existing diagram by dragging and dropping them from the SQL Developer
DB Objects Navigator. You could choose between Information
Engineering (IE) notation and Integration Definition for Information
Modeling (IDEF1X) notation. Schema Visualizer support useful features
like synchronizing existing model with any database, auto layout model
to make it clearer to view, exporting model to graphic file format,
printing, adding small notes and much more.

Please have a look at http://www.sumsoftsolutions.com/erd4sqldev/