The Zend_Pdf class represents PDF documents and provides document-level operations. To create a new document, a new Zend_Pdf object should first be created. Zend_Pdf class also provides two static methods to load an existing PDF document. These are the Zend_Pdf::load() and Zend_Pdf::parse() methods. Both of them return Zend_Pdf objects as a result or throw an exception if an error occurs. The PDF file format supports incremental document update. Thus each time a document is updated, then a new revision of the document is created. Zend_Pdf component supports the retrieval of a specified revision. A revision can be specified as a second parameter to the Zend_Pdf::load() and Zend_Pdf::parse() methods or requested by calling the Zend_Pdf::rollback() method. Zend_Pdf::rollback() method must be invoked before any changes are applied to the document, otherwise the behavior is not defined. call. revisions(); $pdf3->rollback($revisions - 1); ... ]]>