4. The method of claim 2 , wherein propagating child counts comprises: selecting, in turn, each of the tokens of the page; storing, with each token that is part of a list, the child count that has been computed for the start tag token of that token's tightest enclosing list; storing, with each token that is part of a table, the child count, child table count, and child list count that has been computed for the start tag token of that token's tightest enclosing table; and storing, with each token that is part of a paragraph, the child count that has been determined for the start tag token of that paragraph.
2. The method of claim 1 , wherein marking as editable some number of the tokens comprises: labeling the token according to the type of item sequence to be converted and a location of the token within the type of item sequence, where the type of item sequence to be converted includes at least a table, list, sequence of paragraphs, or other type of document regions; counting children of item sequences that are of the type to be converted; propagating child counts of the item sequences; marking, as non-editable, some of the lists, tables, and paragraphs based on the content and relative order of the respective lists, tables, and paragraphs; and marking existing forms, within the first document, as document regions with preserved existing functionality.