Represents a destination in a PDF file. Destinations take 3 forms:
- An explicit destination, which contains a reference to a page as well as some stuff about how to fit it into the window.
- A named destination, which uses the PDF file's Dests entry in the document catalog to map a name to an explicit destination
- A string destintation, which uses the PDF file's Dests entry. in the name directory to map a string to an explicit destination.
All three of these cases are handled by the getDestination() method.