5. A method, comprising: obtaining an image of at least a portion of a document; processing the image to determine a plurality of image characteristics of the image wherein the plurality of image characteristics comprise at least one of a first image characteristic representing ascending letters in the image, a second image characteristic representing descending letters in the image, a third image characteristic representing a number of letters in a word in the image and a fourth image characteristic representing a number of words in a line of text in the image; and identifying a previously stored source document based at least in part on the plurality of image characteristics.
5. A method, comprising: obtaining an image of at least a portion of a document; processing the image to determine a plurality of image characteristics of the image wherein the plurality of image characteristics comprise at least one of a first image characteristic representing ascending letters in the image, a second image characteristic representing descending letters in the image, a third image characteristic representing a number of letters in a word in the image and a fourth image characteristic representing a number of words in a line of text in the image; and identifying a previously stored source document based at least in part on the plurality of image characteristics. 9. The method of claim 5 , wherein the plurality of image characteristics comprises: a series of relative text heights along a top edge of a sequence of characters in the image.