说明：  这本书提供了对PDF文件格式的描述，主要面向直接创建PDF文件的PDF生产者应用程序的开发人员。它还包含足够的信息，允许开发人员编写PDF消费者应用程序，读取现有的PDF文件并解释或修改其内容。
(This book provides a description of the PDF file format and is intended primarily for developers of PDF producer applications that create PDF files directly. It also contains enough information to allow developers to write PDF consumer applications that read existing PDF files and interpret or modify their contents.)