Insert or Delete Text/Image Watermark in PDF File using C#

Add_Image_Watermark.cs

// Load input PDF document
Document pdfDocument = new Document(dataDir + "Input.pdf");

// Access any page of the input PDF
Page testpage = pdfDocument.Pages[1];

// Create image stamp
ImageStamp imageStamp = new ImageStamp(dataDir + "aspose-logo.png");
imageStamp.Background = true;
imageStamp.Height = 300;
imageStamp.Width = 300;

// Center adjust the image watermark based on page dimensions
imageStamp.XIndent = (testpage.PageInfo.Width / 2) - (imageStamp.Width / 2);
imageStamp.YIndent = (testpage.PageInfo.Height / 2) - (imageStamp.Height / 2);
imageStamp.Opacity = 0.5;

// Set stamp id for deleting the watermark later, if required
imageStamp.setStampId(12345678);

// Add stamp to particular page
//pdfDocument.Pages[1].AddStamp(imageStamp);

// Add stamp to each page of PDF
foreach (Page page in pdfDocument.Pages)
{
    page.AddStamp(imageStamp);
}

dataDir = dataDir + "Add_Image_Watermark.pdf";

// Save output document
pdfDocument.Save(dataDir);

Add_Text_Watermark.cs

// Open document
Document pdfDocument = new Document(dataDir + "Input.pdf");

// Create text stamp
TextStamp textStamp = new TextStamp("CONFIDENTIAL");
// Set origin
textStamp.XIndent = 25;
textStamp.YIndent = 400;

// Set text properties
textStamp.TextState.Font = FontRepository.FindFont("Arial");
textStamp.TextState.FontSize = 72.0F;
textStamp.TextState.FontStyle = FontStyles.Italic;
textStamp.TextState.ForegroundColor = Aspose.Pdf.Color.FromRgb(System.Drawing.Color.Gray);
textStamp.Opacity = 50;

// Set Stamp ID for text watermark to later identify it
textStamp.setStampId(123456);

// Add stamp to particular page
pdfDocument.Pages[1].AddStamp(textStamp);

dataDir = dataDir + "Add_Text_Watermark.pdf";
// Save output document
pdfDocument.Save(dataDir);

Remove_Watermark.cs

// Initialize PdfContentEditor class object
PdfContentEditor contentEditor = new PdfContentEditor();

// Call BindPdf method
contentEditor.BindPdf(dataDir + "Watermark.pdf");

// Delete watermark using specific id
contentEditor.DeleteStampById(12345678);

// Save output PDF with removed watermark
contentEditor.Save(dataDir + @"Remove_Watermark.pdf");