Returns a view of the number tree whose root node is root.
public PdfNumberTree? GetNumberTree(CosObject? root)
The root node dictionary, or a reference to it, from this document.
null when root is null or resolves to null, or,
with a diagnostic, to something other than a dictionary.
ISO 32000-2 §7.9.7. For number trees such as the catalog's PageLabels or a structure tree's ParentTree. Views of
the same root share one reader.