通过 .NET SDK 加密 PDF

    using Aspose.Pdf.Cloud.Sdk.Api;
    using Aspose.Pdf.Cloud.Sdk.Model;

    namespace EncryptDecrypt
    {
        public class EncryptPdf
        {
            private string ToBase64(string str)
            { // Convert string to Base64. 
                var bytes = Encoding.UTF8.GetBytes(str);
                return Convert.ToBase64String(bytes);
            }

            public static async Task Encrypt(EncryptDecryptHelper helper, string documentName, string outputName, string localFolder, string remoteFolder)
            { // Get your AppSid and AppSecret from https://dashboard.aspose.cloud (free registration required). 
		pdfApi = new PdfApi(AppSecret, AppSid);

                using (var file = File.OpenRead(Path.Combine(localFolder, documentName)))
		{ // Upload the local encrypted PDF to cloud storage folder name.
                    FilesUploadResult uploadResponse = await pdfApi.UploadFileAsync(Path.Combine(remoteFolder, documentName), documentName);
                    Console.WriteLine(uploadResponse.Uploaded[0]);
                }

                string userPassword = "User-Password";
                string ownerPassword = "Owner-Password";

                // Encrypt the PDF on cloud storage.
                AsposeResponse response = await pdfApi.PostEncryptDocumentInStorageAsync(
                    documentName,
                    ToBase64(userPassword),
                    ToBase64(ownerPassword),
                    CryptoAlgorithm.AESx256.ToString(),
                    folder: remoteFolder);

                // Checks the response and logs the result.
                if (response == null)
                    Console.WriteLine("EncryptPdf(): Unexpected error!");
                else if (response.Code < 200 || response.Code > 299)
                    Console.WriteLine("EncryptPdf(): Failed to encrypt document.");
                else
                {  // Downloads the updated file for local use.
                    Console.WriteLine("EncryptPdf(): document '{0} successfully encrypted.", documentName);
                    Stream stream = pdfApi.DownloadFile(Path.Combine(remoteFolder, documentName));
                    using var fileStream = File.Create(Path.Combine(localFolder, "encrypt_" + outputName));
                    stream.Position = 0;
                    await stream.CopyToAsync(fileStream);
                    Console.WriteLine("EncryptPdf(): File '{0}' successfully downloaded.", "encrypt_" + outputName);
               }
            }
        }
    }