There is a plug-in for Enterprise Architect that does it. Of course, that is much, much more capable than Erwin, but you may not be interested in the capability. You can also look at
http://www.oehive.org/ABL2UML , but that is even more yet.
Note that the intrinsic problem of building a diagram from the OpenEdge schema is that the schema does not include table to table relationships like some schemas do. This means that you need to establish those relationships by some other process. The plugin on PSDN has a "relationship guesser" based on looking for matching field names, but that has some obvious limitations including:
1. It won't find Customer.ID linking to Order.CustomerID and the like.
2. If you have Order.ShipToID and Order.BillToID it can't find both (or either)
3. It won't work on databases with table prefixes on field names.
4. It will blow up if you have commonly named audit fields like DateLastChanged.
Unfortunately, there is no source for the relationship guesser so you can't fix those.
ABL2UML does show you the empirical uses of each table and thus would provide the needed information, but there is no automation.