You can use the Keep away all objects button in PDF Trap Editor to apply a keepaway trap (also called a reverse trap) to all of the objects on a page.

1. From within the PDF Trap Editor session, in the PDF Trap Editor toolbar, click the Keep away all objects  button.
2. In the Keepaway dialog box, specify trap Width and Height parameters.
3. If needed, specify Line Join Style and Miter Limit.
4. Click Keep away all objects.

All traps in the page are deleted, and a knockout trap is added between adjacent objects painted by different inks. That is, each object is painted by at least one ink that does not paint the other.
The figures demonstrates the rule: the background is a mixture of cyan, magenta, and yellow, and the characters are pure cyan, magenta, yellow, and black. There are keepaway traps between the characters, and between the black and the background, but not between the cyan, magenta, or yellow and the background. The knockout trap lets the substrate show through.