1. A method of immediately updating a machine translation system with post-edits during translation of a document, using a machine translation system that comprises a processor and a memory for storing logic that is executed by the processor to perform the method, comprising: receiving a post-edited machine translated sentence pair, the post-edited machine translated sentence pair comprising a source sentence unit and a post-edited target sentence unit; updating a machine translation model by: performing an alignment of the post-edits of the machine translated sentence pair to generate phrases; and adding the phrases to the machine translation model; adapting a language model from the post-edited target sentence unit; calculating translation statistics for the post-edits; adjusting translation weights using the translation statistics while generating test machine translations of the machine translated sentence pair until one of the test machine translations approximately matches the post-edits for the machine translated sentence pair; and retranslating remaining machine translation sentence pairs that have yet to be post-edited using the updated machine translation model and the adjusted translation weights.