1. A method of identifying original document type for scanned documents, comprising: extracting text in a document page; classifying text objects as a function of text object size; classifying page orientation as a function of statistics of text aspect ratio and neighboring character distance; generating a text column structure index; determining whether the document page was originally created using a slide show presentation application, or one of a word processing application and a spreadsheet application, as a function of one or more of the object size classification, text size classification, page orientation classification, and the text column structure index.