The UDF Specifications are available as free PDF files from OSTA at:

http://www.osta.org/specs/

Many IEC/ISO standards that they reference are co-published by ECMA.
For example, Ecma publication ECMA-167 is also approved as ISO/IEC 13346.
They are available as free PDF files from ECMA at:

http://www.ecma-international.org/publications/