User Defined Data Types (UDF) is one of the useful concepts in SQL Server. However UDF can't be modified after they are being used. You would have to remove your User Defined Data Type from each table before you can change it. This will be a big job under certain circumstances.
This procedure changes all tables when you change the UDF.
At present I do this only for Tables. This procedure will work only if only tables refer the UDF.
A short but interesting article, the author has figured out a way to create a PDF from a stored procedure without using a third party library.