Gets the node's text: on each page, its glyphs' text with words separated by one space and lines by one line feed (U+000A), as PlainText joins them; the pages' texts joined by a line feed. Empty when it shows no text.
public string Text { get; }
ISO 32000-2 §9.10, §14.8.2.6.2 and §14.9.4 (replacement text is applied, as ExtractText() does).