How to split the landscape page to portrait in WinForms PDF?

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

string file = "../../Data/InputDoc.pdf";

// Load the existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(file);

// Create a new PDF document.
PdfDocument document = new PdfDocument();

for (int i = 0; i < loadedDocument.Pages.Count; i++)
{
    // Load the page.
    PdfLoadedPage loadedPage = loadedDocument.Pages[i] as PdfLoadedPage;

    if (loadedPage.Size.Width > loadedPage.Size.Height)
    {
        // Create the template from the page.
        PdfTemplate template = loadedPage.CreateTemplate();

        // Calculate the width in inches.
        float width = template.Width / 2;

        // Set the document margin and height.
        document.PageSettings.Height = loadedPage.Size.Height;
        document.PageSettings.Width = width;
        document.PageSettings.Margins.All = 0;

        // Add the page to a new PDF document.
        PdfPage page = document.Pages.Add();

        // Create graphics.
        PdfGraphics graphics = page.Graphics;

        // Draw the template.
        graphics.DrawPdfTemplate(template, new PointF(0, 0));

        // Add another page.
        page = document.Pages.Add();

        // Draw the template.
        page.Graphics.DrawPdfTemplate(template, new PointF(-page.GetClientSize().Width / 2, 0));
    }
    else
    {
        // Import the page into the new PDF document.
        document.ImportPage(loadedDocument, i);
    }
}

// Save the PDF document.
string fileName = "Sample.pdf";
document.Save(fileName);

// Close the document.
document.Close(true);
loadedDocument.Close(true);

// Open the PDF file and view the result in the default PDF viewer.
Process.Start(fileName);

Dim file As String = "../../Data/InputDoc.pdf"

' Load the existing PDF document.
Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument(file)

' Create a new PDF document.
Dim document As PdfDocument = New PdfDocument()

For i As Integer = 0 To loadedDocument.Pages.Count - 1

    ' Load the page.
    Dim loadedPage As PdfLoadedPage = TryCast(loadedDocument.Pages(i), PdfLoadedPage)

    If loadedPage.Size.Width > loadedPage.Size.Height Then

        ' Create the template from the page.
        Dim template As PdfTemplate = loadedPage.CreateTemplate()

        ' Calculate the width in inches.
        Dim width As Single = template.Width / 2
        ' Set the document margin and height.
        document.PageSettings.Height = loadedPage.Size.Height
        document.PageSettings.Width = width
        document.PageSettings.Margins.All = 0

        ' Add the page to a new PDF document.
        Dim page As PdfPage = document.Pages.Add()

        ' Create graphics.
        Dim graphics As PdfGraphics = page.Graphics

        ' Draw the template.
        graphics.DrawPdfTemplate(template, New PointF(0, 0))

        ' Add another page.
        page = document.Pages.Add()

        ' Draw the template.
        page.Graphics.DrawPdfTemplate(template, New PointF(-page.GetClientSize().Width / 2, 0))
    Else

        ' Import the page into the new PDF document.
        document.ImportPage(loadedDocument, i)

    End If
    Next

' Save the PDF document.
Dim fileName As String = "Sample.pdf"
document.Save(fileName)

' Close the document.
document.Close(True)
loadedDocument.Close(True)

' Open the PDF file and view the result in the default PDF viewer.
Process.Start(fileName)