PDFsharp用法：受保护的文档

此示例演示如何使用密码保护文档。 // 获取示例PDF文件的新副本 string filename = "HelloWorld.pdf"; File.Copy(Path.Combine("../../../../PDFs/", filename), Path.Combine(Directory.GetCurrentDirectory(), filename), true);   // 打开现有文档。提供不需要的密码将被忽略。 PdfDocument document = PdfReader.Open(filename, "some text");   PdfSecuritySettings securitySettings = document.SecuritySettings;   // 设置其中一个密码会自动将安全级别设置为pdfdocumentSecurityLevel.Encrypted128位。 securitySettings.UserPassword = "user"; securitySettings.OwnerPassword = "owner";   // 除非出于兼容性原因需要，否则不要使用40位加密 //securitySettings.DocumentSecurityLevel = PdfDocumentSecurityLevel.Encrypted40Bit;   //限制一些权利。 securitySettings.PermitAccessibilityExtractContent = false; securitySettings.PermitAnnotations = false; securitySettings.PermitAssembleDocument = false; securitySettings.PermitExtractContent = false; securitySettings.PermitFormsFill = true; securitySettings.PermitFullQualityPrint = false; securitySettings.PermitModifyDocument = true; securitySettings.PermitPrint = false;   //保存 document.Save(filename); // 预览 Process.Start(filename);