C# .NET 给PDF文件加密设定密码并设置权限

NUGET管理器中引用“pdfsharp”，然后参考如下代码。

// Open an existing document. Providing an unrequired password is ignored.
PdfSharp.Pdf.PdfDocument document = PdfReader.Open(pdfFilePath);
PdfSecuritySettings securitySettings = document.SecuritySettings;
// Setting one of the passwords automatically sets the security level to 
// PdfDocumentSecurityLevel.Encrypted128Bit.
//securitySettings.UserPassword = "user";
securitySettings.OwnerPassword = JinXinConnGuid.ToString();
// 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 = false;
securitySettings.PermitFullQualityPrint = false;
securitySettings.PermitModifyDocument = false;
securitySettings.PermitPrint = true;
// Save the document...
document.Save(pdfFilePath);

参考网站：https://stackoverflow.com/questions/12383409/password-protecting-a-pdf-file