Adobe ACROBAT 3D Manual page 567

3D Measuring preferences
Change the Measuring preferences to determine how 3D data is measured. These options
appear in the Measurement panel of the Preferences dialog box.
Use Scales And Units From Model
Measurements are displayed based on the model units, if present, generated from the
original 3D model. Deselect this option to specify the units of measurements manually.
This setting can be changed in the 3D Measurement Tool palette.
Use Default Display Unit
To use units of measurement that you specify rather than the 3D model's, select this option
and specify a unit of measurement.
3D Measuring Mode
The measuring mode determines what kind of data is measured in the 3D Measurement
Tool palette. (See 3D measuring types.)
3D Measuring Line Color
Specifies the color of the line that appears when you click or drag to measure an object.
3D Snap Settings
Select Snap To 3D Settings to turn on snap. Specify whether points, arcs, edges, or
silhouette edges are snapped to. For Sensitivity, indicate how close the pointer needs to be
to the item being snapped to. For Snap Hint Color, specify the color of the snap line that
appears when you hold the pointer over the 3D object.