This documentation can take the form of notes to the file, marginal notes on draft documents, comments in interim or final reporting letters, or even in an email message. (slaw.ca)
And the original is not really altered, they just add marginal notes (as in, literally, notes in the margin of the page) to it. (politics.stackexchange.com)
This was very easy to do using a stylus to mark the transcript and to make hand written marginal notes where necessary. (slaw.ca)