A reference library can be described as a corpus of an individual composition of documents containing related work of research, documents of favorite authors, or proceedings of a conference. The documents in the corpus may change over time; new documents extend the corpus while other documents are sorted out. A subset of documents may contain meaningful annotations describing their content while other documents contain only weakly annotations. Enriching documents with meaningful annotations is beneficial for the performance of applications like semantic search, content aggregation, automated relationship discovery, query answering and information retrieval. However, enriching and maintaining a document with meaningful annotations is non-trivial. Available (semi-) automatic annotation tools ignore the individual composition of documents in corpora by annotating documents with generic named-entity related data. In this paper, we present techniques for enriching and maintaining annotations for document-specific databases considering changes in the composition of documents.