This book constitutes the thoroughly refereed post-workshop proceedings of the Third International Workshop on Principles of Document Processing, PODP'96, held in Palo Alto, California, USA, in September 1996. The book contains 13 revised full papers presented as chapters of a coherent, monograph-like book. The papers focus equally on the theory and the practice of document processing. Among the topics covered are theory of media, cross media publishing and multi-modal documents, SGML content models, grammar-compatible stylesheets, multimedia documents, temporal constraints in multimedia, hypertext representation, contextual knowledge, structured documents for IR, Web-publishing, virtual documents, etc.