Gets the document's output intents (OutputIntents, PDF 1.4), in the order written; empty when it has none.
public IReadOnlyList<PdfOutputIntent> OutputIntents { get; }
ISO 32000-2 §7.7.2, Table 29, and §14.11.5. Read on every call; the same PdfOutputIntent is returned for the same dictionary. A page's own output intents (OutputIntents) take precedence for that page.