Vertical and horizontal units can be selected independently, on global level, application level or palettes level.

Vertical units

Used for Y positions and height of page objects, vertical rulers, vertical margins and page height, and typographical values in text editing.

Horizontal units

Used for X positions, horizontal rulers, and width of page objects, horizontal margins and page width.

Have in mind that the default vertical and horizontal units drive display of values.

When entering values, you can always override defaults by entering any available unit, e.g. even if your palette is set to display values in inches, you can enter "12pt" or "12000m" or any other unit.