Undo Preferences

The Undo tab controls some settings of the Undo and Redo commands, as well as one setting for the History palette

Undo and Redo Settings

To enable Paint Shop Pro to undo actions, mark the Enable the undo system check box. This enables you to set all the items in this area of the Undo tab.
When the undo system is active, you can set the following options:
Limit undo/redo disk usage to n MBytes of storage per open image Sets the maximum amount of disk space each images undo/redo steps can use.
Limit undo/redo to n steps per open image Sets the number of undoable/redoable steps in each open image. The default value is 250. Steps older than 250 will become undoable steps, only 10 of which will be retained as defined by the Non-undoable steps after last undoable step setting.
Compress undo/redo information Marking this check box saves disk space, but slows down undo and redo operations.
Enable the redo system Activates the Redo command, allowing you to redo actions you have undone.

n Non-undoable steps after last undoable step Sets the number of non-undoable steps that will be retained after the last non-undoable step limit has been reached. The default value is 10.