WPF provides an annotation feature that allows you to add comments and highlights to flow documents and fixed documents. These annotations can be used to suggest revisions, highlight errors, or flag important pieces of information.
Many products provide a wide range of annotation types. For example, Adobe Acrobat allows you to draw revision marks and shapes on a document. WPF isn't quite as flexible. It allows you to use two types of annotations:
Highlighting. You can select some text and give it a colored background of your choice. (Technically, WPF highlighting applies a partially transparent color over your text, but the effect makes it seem as if you were changing the background.)
Sticky notes. You can select some text and attach ...