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 height from 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 a page.
        page = document.Pages.Add();
 
        //Draw a template.
        page.Graphics.DrawPdfTemplate(template, new PointF(-page.GetClientSize().Width/2, 0));
    }
    else
    {
        //Import the pages to the new PDF document.
        document.ImportPage(loadedDocument, i);
    }
}
 
//Save the PDF document.
string fileName = "Sample.pdf";
document.Save(fileName);
 
//Closes the document.
document.Close(true);
loadedDocument.Close(true);
 
//This will open the PDF file and the result will be seen 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 page height.
        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 a page.
        page = document.Pages.Add()
 
        'Draw a template.
        page.Graphics.DrawPdfTemplate(template, New PointF(-page.GetClientSize().Width / 2, 0))
    Else
 
        'Import the pages to a new PDF document.
        document.ImportPage(loadedDocument, i)
 
    End If
Next
 
'Save the PDF document.
Dim fileName As String = "Sample.pdf"
document.Save(fileName)
 
'Closes the document.
document.Close(True)
loadedDocument.Close(True)
 
'This will open the PDF file and the result will be seen in the default PDF viewer.
Process.Start(fileName)