借助于 openoffice 来实现各种文档、资源的PDF格式实时在内存中的转换；然后在内存中实时将某一页再转换成可伸缩的图片展现到浏览器中；实现即可以浏览文档；又能够无法拷贝（模仿豆丁网）-With openoffice to achieve a variety of documents and resources in PDF format for real-time conversion in the memory and th