With increasing knowledge the process of knowledge management and engineering becomes more and more important. Enriching documents by using markup techniques and by supporting semantic annotations is a major technique for knowledge management. This invaluable information is of extreme importance in the context of civil engineering, product life cycle management, virtual archival storage, and preservation. In these fields of applications annotation techniques for 3D documents are a vital part. They provide semantic information, that make up the basis for digital library services: retrieval, indexing, archival, and searching. Furthermore, metadata are of significant importance as they set the stage for data re-use and they provide documentation of data sources and quality, which is vital for every engineering department. Using metadata helps the user to understand data. Additional information allows focusing on key elements of data helps to determine the data's fitness for a particular use and may provide consistency in terminology. In this paper we give an overview on state-of-the-art annotation techniques focussed on 3D data.