Add Signature to PDF in .NET SDK

    using Aspose.Pdf.Cloud.Sdk.Model;

    namespace Signatures
    {
        public class AddSignature
        {
            public static async Task Append(string documentName, string fieldName, string outputName, 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 PDF to cloud storage folder name.
                    FilesUploadResult uploadResponse = await pdfApi.UploadFileAsync(Path.Combine(remoteFolder, documentName), documentName);
                    Console.WriteLine(uploadResponse.Uploaded[0]);
                }

                // Create new signature with parameters for the PDF document on cloud storage.
                Signature signature = new Signature(
                    SignaturePath: CERTIFICATE_PFX,
                    SignatureType: SignatureType.PKCS7,
                    Password: YOUR_CERTIFICATE_PASSWORD,
                    Contact: YOUR_CERTIFICATE_CONTACT,
                    Location: YOUR_CERTIFICATE_LOCATION,
                    Visible: true,
                    Rectangle: new Rectangle(100, 100, 200, 200),
                    FormFieldName: YOUR_SIGNATURE_FORM_FIELD,
                    Authority: YOUR_CERTIFICATE_ISSUER,
                    Date: "08/22/2025 12:15:21.000 PM",
                    ShowProperties: false);

                SignatureField field = new SignatureField(
                    PageIndex: 1,
                    Signature: signature,
                    PartialName: fieldName,
                    Rect: new Rectangle(100, 100, 200, 200));

                // Append signature for the PDF document on cloud storage.
                AsposeResponse response = await pdfApi.PostSignatureFieldAsync(documentName, field, folder: remoteFolder);

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