You don't have to look through dozens of pages. As soon as you select your fare, in the upper right corner where it shows your Cart and gives you the total price, click on "Fare conditions". It pops out a small window with a fare summary (6 sections, total of 10 bullet points), one of which is:
"Changes

• BEFORE DEPARTURE: Changes are permitted free of charge*
  * on condition that seats in the same booking class as your existing ticket are still available on the new flight and/or original fare is still available for a new flight."