افزودن واترمارک از طریق C#

    doc = new Aspose.Pdf.Document("1.pdf");

    artifact = new Aspose.Pdf.WatermarkArtifact();
    artifact.SetImage(new FileStream("1.jpg", FileMode.Open));

    artifact.ArtifactHorizontalAlignment = Aspose.Pdf.HorizontalAlignment.Center;
    artifact.ArtifactVerticalAlignment = Aspose.Pdf.VerticalAlignment.Center;
    artifact.Rotation = 15;
    artifact.Opacity = 1;
    artifact.IsBackground = true;
    doc.Pages[1].Artifacts.Add(artifact);

    //save result pdf to file
    doc.Save("add_watermark.pdf", Aspose.Pdf.SaveFormat.Pdf);