PdfVerticalMetrics

Where one glyph of vertical text sits on the pen, and how far it moves the pen, in thousandths of an em (ISO 32000-1, 9.7.4.3). PdfFont.verticalMetrics gives it.

A glyph in vertical writing has two origins. Its horizontal origin is the one its outline is drawn from. Its vertical origin sits on the pen, and the position vector (vx, vy) leads from the first to the second. A renderer therefore draws the outline at the pen minus that vector, then moves the pen by displacement.