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. ^[1] Zend_Pdf::rollback() call.