密码保护PDF文件

PDFSharp 应该能够使用密码保护PDF文件:

// Open an existing document. Providing an unrequired password is ignored.
PdfDocument document = PdfReader.Open(filename, "some text");

PdfSecuritySettings securitySettings = document.SecuritySettings;

// Setting one of the passwords automatically sets the security level to 
// PdfDocumentSecurityLevel.Encrypted128Bit.
securitySettings.UserPassword  = "user";
securitySettings.OwnerPassword = "owner";

// Don't use 40 bit encryption unless needed for compatibility reasons
//securitySettings.DocumentSecurityLevel = PdfDocumentSecurityLevel.Encrypted40Bit;

// Restrict some rights.
securitySettings.PermitAccessibilityExtractContent = false;
securitySettings.PermitAnnotations = false;
securitySettings.PermitAssembleDocument = false;
securitySettings.PermitExtractContent = false;
securitySettings.PermitFormsFill = true;
securitySettings.PermitFullQualityPrint = false;
securitySettings.PermitModifyDocument = true;
securitySettings.PermitPrint = false;

// Save the document...
document.Save(filename);

参考文献:
http://www.pdfsharp.net/wiki/ProtectDocument-sample.ashx

仅适用于.NET Core/.NET 5及更高版本

PdfSharp 仅适用于 旧的.NET框架 。
PdfSharpCore 同一个库刚刚移植到新的吗 .NET(.NET核心) 。

以上内容 answer by @Daniel Hilgarth 仍然可以工作,而不会对带有移植库的代码进行任何更改。

注释 这个图书馆在 MIT LICENSE ,所以没什么好担心的。