How this works
A PDF LinkAnnotation is only an invisible clickable hotspot — it renders no text of its own. Showing visible, clickable link text normally takes two steps: create a text annotation, then draw a link over it. This sample fuses both into one action: the Add Link button collects the text, color, and URL, and a single instance.create([...]) call adds a TextAnnotation (the visible label) and a LinkAnnotation (a URIAction) sharing one bounding box.