A system and method for identifying a document based on a spectral analysis of the text of the document is described. In some examples, the system generates a document identifier for a rendered document based on assigning values to words in the rendered document, such as values associated with the frequency of use of the word by the rendered document, the absolute or relative position of the word in the rendered document, and so on. The system may use the document identifier to generate a group of documents having similar document identifiers, and choose a likely match from the group of documents based on predictive analysis.