"To document the changes" means to record and keep a record of any modifications or alterations that have been made to something, such as documenting any changes made to a project, process, or document. Full definition
The book focuses on students as an important part of the research teams assisting scientists in documenting the changes in our environment. (dawnpub.com)
I had been asked to fix it on the punch list of document changes. (legaltalknetwork.com)
By this time, the resident physicians were documenting changes on the fetal monitor and had begun the plaintiff on oxygen to assist the fetus. (lubinandmeyer.com)