Binding Margins, Virtual Plotter, Fractional Widths disappeared in Mac OS 10.4 - Tiger.
This problem was fixed, by Apple, in the OS 10.4.3 update.
The Reunion item in the Settings pop-up menu of the Page Setup window disappeared in the initial Tiger (OS 10.4) release. Thus, Reunion-specific settings described in the manual such as binding margins, fractional widths, and the Virtual Plotter were not available.
To correct this problem, install the Mac OS 10.4.3 (or later) update.