16. A computer-implemented system for use in generating a structured electronic document comprising a primary document, one or more supplemental content items and one or more references to the one or more supplemental content items, respectively, the system comprising: a processor; and a computer readable memory having embodied thereon: a candidate content item repository having one or more content items that can be included in a structured electronic document; a copy module for deriving a base supplemental content item from a selected one of the candidate content items and further configured to designate a unique identifier for the base supplemental content item and for deriving an annotated supplemental content item from the base supplemental content item wherein the annotated supplemental content item includes at least a subset of content from the base supplemental content item; a document editor for receiving the unique identifier and to insert the unique identifier into a reference to the base supplemental content in the primary document and to insert another reference including another unique identifier of the annotated supplemental content item into the primary document; and a structured electronic document manager configured to create the structured electronic document by assembling the primary document, the base supplemental content item and the annotated supplement content item.
16. A computer-implemented system for use in generating a structured electronic document comprising a primary document, one or more supplemental content items and one or more references to the one or more supplemental content items, respectively, the system comprising: a processor; and a computer readable memory having embodied thereon: a candidate content item repository having one or more content items that can be included in a structured electronic document; a copy module for deriving a base supplemental content item from a selected one of the candidate content items and further configured to designate a unique identifier for the base supplemental content item and for deriving an annotated supplemental content item from the base supplemental content item wherein the annotated supplemental content item includes at least a subset of content from the base supplemental content item; a document editor for receiving the unique identifier and to insert the unique identifier into a reference to the base supplemental content in the primary document and to insert another reference including another unique identifier of the annotated supplemental content item into the primary document; and a structured electronic document manager configured to create the structured electronic document by assembling the primary document, the base supplemental content item and the annotated supplement content item. 17. The system as recited in claim 16 further comprising a document editor comprising a user interface configured to enable a user to select one of the candidate content items for inclusion into the structured electronic document.