selecting a guide in the list, you can change its settings underneath
Vertical or Horizontal
the page box used as reference, or another guide
The reference point on the page box. Top/Center/Bottom for Horizontal
guides, Left/Center/Right for Vertical guides.
Guide Name: if Relative
to is set to "Other Guide", you can select a guide from
the dropdown. Only guides with the same orientation will be available.
Moving a guide will also move the guide(s) that are "Relative to"
If the "Relative to" guide is removed, the depending
guide’s settings will change to Relative to Media box
from the reference point. A positive value is to the top/right,
a negative value to the bottom/left.
Mirror on even pages (only for
vertical guides): mirror the guide horizontally over the center
line of the crop box on even pages