Work with pages in PDF docuemnts via .NET SDK

    using Aspose.Pdf.Cloud.Sdk.Model;

    namespace Pages
    {
        public class PagesAddImageStamp
        {
            public static async Task Append(string documentName, string outputName, int pageNumber, string imageFileName, float width, float height, 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]);
                }
                using (var file = File.OpenRead(Path.Combine(localFolder, imageFileName)))
		{ // Upload the local image file to cloud storage folder name.
                    FilesUploadResult uploadImageResponse = await pdfApi.UploadFileAsync(Path.Combine(remoteFolder, imageFileName), imageFileName);
                    Console.WriteLine(uploadImageResponse.Uploaded[0]);
                }

                ImageStamp stamp = new ImageStamp(
                    Background: true,
                    HorizontalAlignment: HorizontalAlignment.Center,
                    VerticalAlignment: VerticalAlignment.Top,
                    Opacity: 0.3,
                    Rotate: Rotation.None,
                    RotateAngle: 45,
                    Width: width,
                    Height: height,
                    Zoom: 1,
                    FileName: Path.Combine(remoteFolder, imageFileName));

                // Append new image stamp to page of the PDF on cloud storage.
                AsposeResponse response = await pdfApi.PostPageImageStampsAsync(documentName, pageNumber, new List<ImageStamp> { stamp }, folder: remoteFolder);

                // Checks the response and logs the result.
                if (response == null)
                    Console.WriteLine("PagesAddImageStamp(): Unexpected error!");
                else if (response.Code < 200 || response.Code > 299)
                    Console.WriteLine("PagesAddImageStamp(): Failed to append image stamp to the page of document.");
                else
                { // Downloads the updated file for local use.
                    Console.WriteLine("PagesAddImageStamp(): image '{0}' appended as stamp to the page '{1}' of the document '{2}.", imageFileName, pageNumber, documentName);
                    Stream stream = pdfApi.DownloadFile(Path.Combine(remoteFolder, documentName));
                    using var fileStream = File.Create(Path.Combine(localFolder, "add_page_image_stamp_" + outputName));
                    stream.Position = 0;
                    await stream.CopyToAsync(fileStream);
                    Console.WriteLine("PagesAddImageStamp(): File '{0}' successfully downloaded.", "add_page_image_stamp_" + outputName);
                }
            }
        }
    }