Same as HSB, Cylindrical geometries with hue, their angular dimension,
starting at the red primary at 0°, passing through the green primary
at 120° and the blue primary at 240°, and then wrapping back to red at 360°
This class is the base of the Pdf generator. A PdfDocument class is
created for a document, and each page, object, annotation,
etc is added to the document.
Once complete, the document can be written to a Stream, and the Pdf
document's internal structures are kept in sync.
