1. A method for processing data captured from a rendered document, the method comprising: receiving data specifying a user input selecting a portion of content of a rendered document, the selected document portion containing text; determining an encoded representation of text contained by the selected document portion, wherein determining the encoded representation of text contained by the selected document portion comprises determining a sequence of offsets that represent the text, and wherein each offset represents a number of character positions separating recurring instance of each letter within the text of the selected document portion; searching for the encoded representation of text within a corpus of electronic documents to identify (1) an electronic document contained in the corpus of electronic documents, the identified electronic document containing the selected document portion, and (2) a position within the identified electronic document at which the selected document portion occurs; and providing, for presentation on a display device, a menu of selectable user actions associated with the identified position in the identified electronic document, wherein at least one of the selectable user actions was associated with the identified position before the receipt of the data specifying the user input.