เพิ่มแสตมป์หน้าลงใน PDF ผ่าน C#

static Aspose.Pdf.PdfPageStamp GetPageStamp(int pageNum)
{
    var pageStampFile = Path.Combine(dataDir, "PageStamp.pdf");
    return new Aspose.Pdf.PdfPageStamp(pageStampFile, pageNum)
    {
        Height = 800,
        Background = true
    };
}

var inputFile = Path.Combine(dataDir, "sample.pdf");
var outputFile = Path.Combine(dataDir, "AddPageStamp_out.pdf");        
var pdfDocument = new Aspose.Pdf.Document(inputFile);
var bluePageStamp = GetPageStamp(1);
var plumPageStamp = GetPageStamp(2);

for (int i = 1; i < 5; i++)
{
    if (i % 2 == 0)
        pdfDocument.Pages[i].AddStamp(bluePageStamp);
    else
        pdfDocument.Pages[i].AddStamp(plumPageStamp);            
}
pdfDocument.Save(outputFile);