An action whose type Table 201 does not list, such as an extension's; every listed type has its own model.
public sealed class PdfUnknownAction : PdfAction
ISO 32000-2 §12.6.4.1, Table 201. Kept as it is (parse-and-preserve) and reachable through Dictionary; ActionType says which type it is.
kind:method, kind:property, kind:ctor. Press Esc to clear.KindGets the type of action ActionType names in Table 201, or Unknown.