Annotations may contain properties that describe their appearance — such as annotation color or shape. However, these don’t guarantee that the annotation will be displayed the same in different PDF viewers. To solve this problem, each annotation can define an appearance stream that should be used for rendering the annotation.
When you modify the annotation properties, you must call the
updateAp() method in the
public boolean updateAp();
It’s easy to set up an annotation to show a custom appearance stream. This is typically done with stamp annotations because they have few other properties. A stamp annotation used this way is usually called an image annotation.