1. A memory for storing software for comparing a plurality of documents, the software comprising: logic for obtaining a plurality of documents, each of the documents comprising a plurality of graphic elements; logic for associating a plurality of unique element identifiers with the graphic elements of the plurality of documents wherein, upon determining that a first graphic element of a first document is sufficiently similar to a second graphic element of a second document, the method comprises associating the same unique element identifier with both the first graphic element and the second graphic element; logic for organizing the plurality of unique element identifiers into a plurality of lists corresponding to the plurality of documents wherein entries in a list correspond to a display order of graphic elements of a document; and logic for merging a plurality of version documents into a layered document, wherein the plurality of documents comprises a plurality of version documents, each representing a version of a document.