Use the Trapping pane of the Preferences dialog box (QuarkXPress/Edit menu) to set default trapping for Print layouts.

Select a Trapping Method:

• Click Absolute to trap using the values in the Auto Amount and Indeterminate fields according to the object and background colors involved. If the object color is darker, the object is choked by the background using the Auto Amount value. If the object color is lighter, the object is spread into the background using the Auto Amount value.
• Click Proportional to trap using the value in the Auto Amount field multiplied by the difference between the luminance (lightness or brightness) of the object color and the background color.
• Click Knockout All to turn off trapping and print objects with a zero trap amount.
• Check Process Trapping to trap each process separation plate individually when a page contains overlapping process colors.
• Check Ignore White to specify that an object color in front of multiple background colors (including white) does not take white into account when trapping.

Enter a trapping value in the Auto Amount field or choose Overprint:

• Enter a value in the Auto Amount field to control the amount of trapping that QuarkXPress applies to object and background colors that have an Auto Amount specified in the Trap Specifications dialog box (Edit > Colors > Edit Trap), and to control the amount of trapping applied to items with an Auto Amount (+) Trap Information or (–) specified in the Trap Information palette (Window > Trap Information).
• Choose Overprint to cause overprinting for object and background colors with an Auto Amount specified in the Trap Specifications dialog box (Edit > Colors > Edit Trap), as well as for items with an Auto Amount (+) or (–) specified in the Trap Information palette (Window > Trap Information).

Enter a trapping value in the Indeterminate field or choose Overprint:

• Enter a value in the Indeterminate field to control the amount of trapping that QuarkXPress applies to object colors that are in front of indeterminate backgrounds (multiple colors with conflicting trapping relationships).
• Choose Overprint to cause an object color to overprint an indeterminate background.

Enter a Knockout Limit value. The knockout limit is the value (expressed as a percentage of darkness of the object color) that enables you to control the point at which an object color knocks out a background color.

Enter an Overprint Limit value. Overprint limit is a trapping setting that allows an object set to overprint to trap according to the Auto Amount value if the object’s shade is less than a particular percentage.