As an alternative to creating a brand new tdoc, on the pop-up window, you can choose to revise an existing tdoc. To do this, simply click the check-box on the left and enter the original tdoc number (i.e. the number of the tdoc you wish to revise. When you click "prefill", all the meta-data from the original tdoc is copied into the equivalent fields of the new one. However, you can change any of that data, simply by adding to it or overwriting it. The reservation is effected in the same way as for brand new tdocs.