Implementing undo/redo in PDF Studio using object-oriented design pattern

PDF Studio is a software package that provides a visual design environment to help a user create a document with text, images and data from a database, and that generates the file in PDF (Portable Document Format). Undo/redo functionality is a common requirement for most software that has a visual user interface. This paper introduces the implementation of undo/redo in this software package and describes how object-oriented design patterns are applied to its design and implementation.