Thesis pages have words, gaps, lines, margins and space at the top and bottom.
Annotation is a key step in viva preparation: adding something to make what’s there even better for the purposes of the viva. You gain a little help when you do the work because you have to think about what you need to add and why – and you get even more by making a special edition version of your thesis to use in the viva.
Every page in your thesis gives you an opportunity to help yourself but you don’t need to add something to every page or overload every page with more words, underlining and highlighting. The opportunity could be used by thinking, “Actually, this is fine as it is.”
Turn the page. Look carefully. Add what you need.