如何检查PDF是否被修改 [英] How to check if PDF was modified

问题描述

我有一个由第三方系统生成的PDF.我已经使用PDF编辑器或els软件对其进行了修改.
是否可以检测没有原始文件的PDF文件是否被修改?

I have a PDF generated by 3rd party system. Using PDF editor or els software I have modified it.
Is it possible to detect if PDF file was modified, without original file?

我将添加一些详细信息.

I will add some more details.

没有加密，也没有签名功能.

There is no encryption and no signature features.

文档由IT系统创建.用户收到文档并对其进行修改.

Document is created by IT system. User receives document and modifies it.

是否可以以某种方式跟踪更改?

Is it possible to track that change somehow?

我认为所有这些应用程序都将一些数据保留在PDF标头中或文件中编码的某个地方，并且可以检查它.但是Windows资源管理器显示的属性什么也没显示...所以我感兴趣的是，有什么东西比在资源管理器中查看属性/标题更聪明.

I thought that all these applications leaves some data in PDF header or somewhere encoded inside file and it is possible to check it. However properties showed by windows explorer shows nothing... so I was interested if there is something smarter than viewing properties/header in explorer.

推荐答案

问题是，仅在Mac上的预览"中打开PDF并按Command-S保存文件，会将创建日期"和修改日期"替换为匹配当前日期/时间.因此，即使创建日期也将是错误的.即使是新手用户也可以在不知不觉中执行此操作，因此，如果您尝试跟踪可能故意修改文档的人员，则可能会导致误报.

The problem with this is that just opening the PDF on a Mac in Preview and hitting Command-S to save the file will replace both the Creation and Modification date to match the current date/time. So even the creation date will be wrong. Even novice users can unknowingly do this, so if you're trying to track someone who may be purposefully modifying the document, it may lead to a false positive.

不幸的是，您要问的内容太容易被欺骗和愚弄.

What you're asking is just too easy to spoof and fool unfortunately.

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