Gets the document's embedded files: the entries of the name dictionary's EmbeddedFiles tree, in tree order.
public IReadOnlyList<PdfEmbeddedFileEntry> EmbeddedFiles { get; }
ISO 32000-2 §7.7.4, Table 32 (PDF 1.4), and §7.11.4. Read on every call. An entry whose value is not a file specification is
skipped with a FileSpecificationInvalid diagnostic. Files attached only to annotations or associated files are not
listed here (PDF 2.0 Application Note 002 §6.2): see EnumerateAssociatedFiles(Boolean).