How to add the custom border design to an existing PDF document using C#

using Syncfusion.Pdf;
using Syncfusion.Pdf.Graphics;
using Syncfusion.Pdf.Parsing;
using System.Drawing;
using System.IO;

Imports Syncfusion.Pdf
Imports Syncfusion.Pdf.Graphics
Imports Syncfusion.Pdf.Parsing
Imports System.Drawing
Imports System.IO

//Create a new PDF document
PdfDocument doc = new PdfDocument();
doc.PageSettings.Margins.All = 0;
 
//Add a page to the document
PdfPage page = doc.Pages.Add();
 
//Create PDF graphics for the page
PdfGraphics graphics = page.Graphics;
 
//Load the image from the disk
PdfBitmap image = new PdfBitmap("../../Data/certificateborder.png");
 
//Draw the image
graphics.DrawImage(image, 0, 0, page.GetClientSize().Width, page.GetClientSize().Height);
 
//Save the document
MemoryStream ms = new MemoryStream();
doc.Save(ms);
 
//Close the document
doc.Close(true);
 
//Load the border design PDF document 
PdfLoadedDocument loadedDocument1 = new PdfLoadedDocument(ms);
 
//Load the existing PDF document 
PdfLoadedDocument loadedDocument2 = new PdfLoadedDocument("../../Data/Input.pdf");
 
//Create the new document
PdfDocument document = new PdfDocument();
document.PageSettings.Margins.All = 0;
 
//Add the border design in each page of an existing PDF document 
for (int i = 0; i < loadedDocument2.Pages.Count; i++)
{
    //Add PDF page
    PdfPage pdfPage = document.Pages.Add();
 
    //Create a template from the first document
    PdfPageBase loadedPage = loadedDocument1.Pages[0];
    PdfTemplate template = loadedPage.CreateTemplate();
 
    //Draw the loaded template into new document
    pdfPage.Graphics.DrawPdfTemplate(template, PointF.Empty, page.GetClientSize());
 
    //Create a template from the second document
    loadedPage = loadedDocument2.Pages[i];
    template = loadedPage.CreateTemplate();
 
    //Draw the loaded template into new document
    pdfPage.Graphics.DrawPdfTemplate(template, PointF.Empty, page.GetClientSize());
}
 
//Save the PDF document 
document.Save("Sample.pdf");
 
//Close the PDF documents 
document.Close(true);
loadedDocument1.Close(true);
loadedDocument2.Close(true);
 
//This will open the PDF file and the result will be seen in the default PDF Viewer
Process.Start("Sample.pdf");

'Create a new PDF document
Dim doc As PdfDocument = New PdfDocument()
doc.PageSettings.Margins.All = 0
 
'Add a page to the document 
Dim page As PdfPage = doc.Pages.Add()
 
'Create PDF graphics for the page 
Dim graphics As PdfGraphics = page.Graphics
 
'Load the image from the disk 
Dim image As PdfBitmap = New PdfBitmap("../../Data/certificateborder.png")
 
'Draw the image 
graphics.DrawImage(image, 0, 0, page.GetClientSize().Width, page.GetClientSize().Height)
 
'Save the document
Dim ms As MemoryStream = New MemoryStream()
doc.Save(ms)
 
'Close the document
doc.Close(True)
 
'Load the border design PDF document 
Dim loadedDocument1 As PdfLoadedDocument = New PdfLoadedDocument(ms)
 
'Load the existing PDF document 
Dim loadedDocument2 As PdfLoadedDocument = New PdfLoadedDocument("../../Data/Input.pdf")
 
'Create the new document
Dim document As PdfDocument = New PdfDocument()
document.PageSettings.Margins.All = 0
 
'Add the border design in each page of an existing PDF document 
For i As Integer = 0 To loadedDocument2.Pages.Count - 1
    'Add PDF page
    Dim pdfPage As PdfPage = document.Pages.Add()
 
    'Create a template from the first document
    Dim loadedPage As PdfPageBase = loadedDocument1.Pages(0)
    Dim template As PdfTemplate = loadedPage.CreateTemplate()
 
    'Draw the loaded template into new document
    pdfPage.Graphics.DrawPdfTemplate(template, PointF.Empty, page.GetClientSize())
 
    'Create a template from the second document
    loadedPage = loadedDocument2.Pages(i)
    template = loadedPage.CreateTemplate()
 
    'Draw the loaded template into new document
    pdfPage.Graphics.DrawPdfTemplate(template, PointF.Empty, page.GetClientSize())
Next
 
'Save the PDF document 
document.Save("Sample.pdf")
 
'Close the PDF documents 
document.Close(True)
loadedDocument1.Close(True)
loadedDocument2.Close(True)
 
'This will open the PDF file and the result will be seen in the default PDF Viewer
Process.Start("Sample.pdf")