I am the author of a documentation tool for all major DBMS on the market, and I recently added support for Teradata. I have tried it on the sample dbs that Teradata 13 ships with, as well as the system catalog itself (DBC). What I'd really like though are some beta testers to run it against some real world databases.
The tool is called SqlSpec. You give it a connection string to your database, and it generates comprehensive documentation for your db, with PK/FK graphs, dependency graphs, and lots more.
In addition to Teradata, SqlSpec supports 15 other platforms (SQL Server, Oracle, Sybase, Informix, DB2, MySQL, PostgreSQL, etc). As far as I know, SqlSpec is the only tool of its kind that supports Teradata.
If you'd like to try it, you can find it here: http://www.elsasoft.org/download.htm - download the BETA, not the stable release, as Teradata support is still in beta.