11. One or more non-transitory computer-readable media having recorded thereon instructions, that when executed by one or more computer processors, perform operations comprising: receiving an identification of a first composite document, wherein: the first composite document comprises a spreadsheet workbook stored as a data structure on the server system, and the first composite document contains a plurality of distinct sub-documents, wherein one or more of the sub-documents comprises a worksheet of the spreadsheet workbook; receiving at the server system an indication of user intent to copy one of the sub-documents to a second composite document, the indication resulting from a user selection of a name of the one of the sub-documents for copying to the second composite document, wherein the second composite document comprises a spreadsheet workbook stored as a data structure on the server system; identifying one or more composite documents stored on the server system to which a user associated with the remote computing device has access; receiving an indication of a user selection of the second composite document from among the one or more composite documents; and causing the indicated one of the sub-documents to be copied from the first composite document to the second composite document.
11. One or more non-transitory computer-readable media having recorded thereon instructions, that when executed by one or more computer processors, perform operations comprising: receiving an identification of a first composite document, wherein: the first composite document comprises a spreadsheet workbook stored as a data structure on the server system, and the first composite document contains a plurality of distinct sub-documents, wherein one or more of the sub-documents comprises a worksheet of the spreadsheet workbook; receiving at the server system an indication of user intent to copy one of the sub-documents to a second composite document, the indication resulting from a user selection of a name of the one of the sub-documents for copying to the second composite document, wherein the second composite document comprises a spreadsheet workbook stored as a data structure on the server system; identifying one or more composite documents stored on the server system to which a user associated with the remote computing device has access; receiving an indication of a user selection of the second composite document from among the one or more composite documents; and causing the indicated one of the sub-documents to be copied from the first composite document to the second composite document. 17. The non-transitory recordable media of claim 11 , wherein the operations further comprise transforming references in the indicated one of the sub-documents to other sub-documents in the first composite document, so as to aim the references to sub-documents in the second composite document.