Undo/Redo Tools
When editing PDF documents in PDF Plus, you can simply use unlimited Undo and Redo to cancel actions and resume canceled actions, which makes your PDF documents more perfect.
To undo an action in PDF Plus:
Choose Edit > Undo, or select Undo 
on the Edit toolbar. The latest action on the PDF document will be canceled.
Note: Only when you have edited the PDF document, the Undo command is in activation. You cannot undo saved actions.
To redo an action in PDF Plus:
Choose Edit > Redo, or select Redo 
on the Edit toolbar. The latest canceled action on the PDF document will be resumed.
Note: The Redo command can be performed only after an action on the PDF document is canceled. You cannot redo when the document is saved after an action is undone.