There are four basic types of UN documents: periodicals, sales publications, mimeographed/masthead documents, and official records. Periodicals (like the UN Chronicle) can be located by searching the indexes mentioned in this guide. Sales publications include yearbooks and annuals (Yearbook of the United Nations and Yearbook on Human Rights) serials, monographs and special studies. Mimeographed documents include provisional records of meetings, reports, resolutions, and other working documents of the UN organs. Some are republished in final corrected form in the official records or sales publications. Official records contain the meeting records of the UN organs (usually summary records, with the exception of the records of General Assembly and First Committee and Security Council meetings which are verbatim--"proces-verbaux"), annexes contain the text of agenda items (papers submitted to the organs for discussion), and supplements contain reports of subsidiary organs and resolutions. For more information on documents, see the section above on research guides.
The web is a viable vehicle for locating the full-text of documents from about 1993 onwards.
Most document collections are arranged by the document symbol. The basic principle is that documents are identified by the issuing body. The symbols are composed of capital letters and numbers. The first letter(s) indicates the main body of the UN (A/ is the General Assembly, E/ is ECOSOC, etc.). Specific symbols after the first slash indicate the sub-body within the main body (/CN is a commission, /WP is working party, etc.).
The classification system of the United Nations is explained (with lists of the abbreviations) in many of the research guides mentioned above (for example Guide to International Legal Research). The UNDOC: Current Index (MFiche UN DOCS ST/LIB/SER.M/CUM) lists new document symbols. See also the Document Symbols section of the UN web site.