Trimming maps allows you to take a map that contains more information than is necessary for your task and make it smaller. You can trim a full map to a selection window that you make, or trim a map based on the smallest map possible containing all of the feature on a given map.
Trimming a Map to a layer's extent
Select the layer in the Layer Stack
Choose
>Cartographica will remove all data outside of the extent of the selected layer from the map on all layers