How to add cover page to an existing PDF document?

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

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

//Load the PDF document
PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");
//Create a new instance of PdfDocument
PdfDocument document = new PdfDocument();
//Add a section to PDF document
PdfSection section1 = document.Sections.Add();
//Add pages to the section
PdfPage coverpage = section1.Pages.Add();
//Create PDF graphics for the page
PdfGraphics graphics = coverpage.Graphics;
//Set the standard font
PdfFont font = new PdfStandardFont(PdfFontFamily.Helvetica, 20);
//Set the string format with horizontal and vertical alignment
PdfStringFormat format = new PdfStringFormat(PdfTextAlignment.Center, PdfVerticalAlignment.Middle);
//Add vertical distance between the baselines of adjacent lines of text
format.LineSpacing = 2;
RectangleF bounds = new RectangleF(PointF.Empty, coverpage.GetClientSize());
//Draw the text
graphics.DrawString("Essential PDF provides support to add barcodes to the PDF document.", font, PdfBrushes.Black, bounds, format);
PdfSection section2 = document.Sections.Add();
//Add a section to PDF document
for (int i = 0; i < loadedDocument.Pages.Count; i++)
{
    //Get loaded page as template
    PdfTemplate template = loadedDocument.Pages[i].CreateTemplate();
    //Create new page
    PdfPage page = document.Pages.Add();
    //Create Pdf graphics for the page
    PdfGraphics g = page.Graphics;
    //Draw template with the size as loaded page size
    g.DrawPdfTemplate(template, PointF.Empty, page.GetClientSize());
}
//Save and close the document
document.Save("AddCoverPage.pdf");
document.Close(true);
//Close the loaded PDF docuemnt
loadedDocument.Close(true);

'Load the PDF document
Dim loadedDocument As New PdfLoadedDocument("..\..\Data\input.pdf")
'Create a new instance of PdfDocument
Dim document As New PdfDocument()
'Add a section to PDF document
Dim section1 As PdfSection = document.Sections.Add()
'Add pages to the section
Dim coverpage As PdfPage = section1.Pages.Add()
'Create PDF graphics for the page
Dim graphics As PdfGraphics = coverpage.Graphics
'Set the standard font
Dim font As PdfFont = New PdfStandardFont(PdfFontFamily.Helvetica, 20)
'Set the string format with horizontal and vertical alignment
Dim format As New PdfStringFormat(PdfTextAlignment.Center, PdfVerticalAlignment.Middle)
'Add vertical distance between the baselines of adjacent lines of text
format.LineSpacing = 2
Dim bounds As New RectangleF(PointF.Empty, coverpage.GetClientSize())
'Draw the text
graphics.DrawString("Essential PDF provides support to add barcodes to the PDF document.", font, PdfBrushes.Black, bounds, format)
Dim section2 As PdfSection = document.Sections.Add()
'Add a section to PDF document
For i As Integer = 0 To loadedDocument.Pages.Count - 1
    'Get loaded page as template
    Dim template As PdfTemplate = loadedDocument.Pages(i).CreateTemplate()
    'Create new page
    Dim page As PdfPage = document.Pages.Add()
    'Create Pdf graphics for the page
    Dim g As PdfGraphics = page.Graphics
    'Draw template with the size as loaded page size
    g.DrawPdfTemplate(template, PointF.Empty, page.GetClientSize())
Next
'Save and close the document
document.Save("AddCoverPage.pdf")
document.Close(True)
'Close the loaded PDF docuemnt
loadedDocument.Close(True)