C# 对 PDF 文件进行数字签名
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Digitally sign PDF files
提问by Sergio
I have a digital certificate that identifies an user. I need to use it to Digitally sign pdf files.
我有一个识别用户的数字证书。我需要用它来对 pdf 文件进行数字签名。
Does anyone have an example that does not uses a third party component? I need to get this done but it would be nice to fully understand how things are done.
有没有人有一个不使用第三方组件的例子？我需要完成这项工作，但最好能完全了解事情是如何完成的。
C# Examples please :)
C#示例请:)
采纳答案by Darin Dimitrov
The open source iTextSharplibrary will allow you to do this. Here's a postexplaining how to digitally sign a pdf file. If you don't want to use a third party library then you can implement it yourself but it could be a tough task -> you can start by reading the pdf specification(8.6MB)
开源iTextSharp库将允许您执行此操作。这是一篇解释如何对 pdf 文件进行数字签名的帖子。如果您不想使用第三方库，那么您可以自己实现它，但这可能是一项艰巨的任务 -> 您可以从阅读pdf 规范(8.6MB) 开始
回答by Eugene Mayevski 'Callback
Proper PDF signing is a verysophisticated task. There exist a number of files that don't conform to the PDF specification (broken xrefs etc) and your code must handle all of them. Then various Acrobat versions treat certain things in signed fields differently. So if you need to do the task (rather than study how it works) you should rely on third-party solution, such as our PDFBlackboxcomponents.
正确的 PDF 签名是一项非常复杂的任务。存在许多不符合 PDF 规范（损坏的外部参照等）的文件，您的代码必须处理所有这些文件。然后各种 Acrobat 版本以不同的方式处理签名字段中的某些内容。因此，如果您需要完成任务（而不是研究它是如何工作的），您应该依赖第三方解决方案，例如我们的PDFBlackbox组件。
回答by AffineMesh
Digitally signing a PDF document without using a third-party component entails a great deal of work and is generally best avoided.
在不使用第三方组件的情况下对 PDF 文档进行数字签名需要大量工作，通常最好避免。
Components do all the hard work for you, so you don't have to. You should find there are some excellent free PDF components available that will suit your needs.
组件会为您完成所有繁重的工作，因此您不必这样做。您应该会发现有一些优秀的免费 PDF 组件可以满足您的需求。
The following example written in C# shows how simple it is to digitally sign a PDF document using ABCpdf:
以下用 C# 编写的示例显示了使用 ABCpdf 对 PDF 文档进行数字签名是多么简单：
Doc theDoc = new Doc();
theDoc.Read(Server.MapPath("../Rez/Authorization.pdf"));
Signature theSig = (Signature)theDoc.Form["Signature"];
theSig.Location = "Washington";
theSig.Reason = "Schedule Agreed";
theSig.Sign(Server.MapPath("../Rez/JohnSmith.pfx"), "111111");
theDoc.Save(Server.MapPath("Signed.pdf"));
