1. A computer-implemented method comprising: obtaining an image of a paper document; detecting data fields on the image corresponding to a document type; generating by a processor of a data capture system a flexible document description for the document type based on the detected data fields, including creating a set of search elements for each data field, each search element having one or more associated search criteria; and training the flexible document description using a search algorithm to detect the data fields on additional training images based on the set of search elements.