PM> Install-Package Spire.PDF

using Spire.Pdf;

namespace RearrangePDF
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a PdfDocument object
            PdfDocument pdf = new PdfDocument();

            //Load a sample PDF document
            pdf.LoadFromFile("input.pdf");

            //Rearrange pages by page index
            pdf.Pages.ReArrange(new int[] { 1, 0, 2, 3 });

            //Save the document
            pdf.SaveToFile("ChangeOrder.pdf");
            pdf.Close();
        }
    }
}

Imports Spire.Pdf

Namespace RearrangePDF
    Class Program
        Private Shared Sub Main(ByVal args As String())

            'Create a PdfDocument object
            Dim pdf As PdfDocument = New PdfDocument()

            'Load a sample PDF document
            pdf.LoadFromFile("input.pdf")

            'Rearrange pages by page index
            pdf.Pages.ReArrange(New Integer() {1, 0, 2, 3})

            'Save the document
            pdf.SaveToFile("ChangeOrder.pdf")
            pdf.Close()
        End Sub
    End Class
End Namespace

PM> Install-Package Spire.PDF

using Spire.Pdf.AutomaticFields;
using Spire.Pdf.Graphics;
using Spire.Pdf;
using System.Drawing;
using Spire.Pdf.License;

namespace AddPageNumbersToLeftCorner
{
    class Program
    {
        static void Main(string[] args)
        {
            // Apply your license key
            LicenseProvider.SetLicenseKey("License Key");

            // Create a PdfDocument object
            PdfDocument doc = new PdfDocument();

            // Load a PDF file
            doc.LoadFromFile("C:\\Users\\Administrator\\Desktop\\Terms of service.pdf");

            // Create font, brush and pen, which determine the appearance of the page numbers to be added
            PdfTrueTypeFont font = new PdfTrueTypeFont(new Font("Times New Roman", 12, FontStyle.Regular), true);
            PdfBrush brush = PdfBrushes.Black;
            PdfPen pen = new PdfPen(brush, 1.0f);

            // Create a PdfPageNumberField object and a PdfPageCountField object
            PdfPageNumberField pageNumberField = new PdfPageNumberField();
            PdfPageCountField pageCountField = new PdfPageCountField();

            // Create a PdfCompositeField object to combine page count field and page number field in a single field
            PdfCompositeField compositeField = new PdfCompositeField(font, brush, "Page {0} of {1}", pageNumberField, pageCountField);

            // Get the page size
            SizeF pageSize = doc.Pages[0].Size;

            // Set the location of the composite field
            compositeField.Location = new PointF(72, pageSize.Height - 45);

            // Iterate through the pages in the document
            for (int i = 0; i < doc.Pages.Count; i++)
            {

                // Get a specific page
                PdfPageBase page = doc.Pages[i];

                // Draw a line at the specified position
                page.Canvas.DrawLine(pen, 72, pageSize.Height - 50, pageSize.Width - 72, pageSize.Height - 50);

                // Draw the composite field on the page
                compositeField.Draw(page.Canvas);
            }

            // Save to a different PDF file
            doc.SaveToFile("AddPageNumbersToLeftCorner.pdf");

            // Dispose resources
            doc.Dispose();
        }
    }
}

using Spire.Pdf.AutomaticFields;
using Spire.Pdf.Graphics;
using Spire.Pdf;
using System.Drawing;
using Spire.Pdf.License;

namespace AddPageNumbersToCenter
{
    class Program
    {
        static void Main(string[] args)
        {
            // Apply your license key
            LicenseProvider.SetLicenseKey("License Key");

            // Create a PdfDocument object
            PdfDocument doc = new PdfDocument();

            // Load a PDF file
            doc.LoadFromFile("C:\\Users\\Administrator\\Desktop\\Terms of service.pdf");

            // Create font, brush and pen, which determine the appearance of the page numbers to be added
            PdfTrueTypeFont font = new PdfTrueTypeFont(new Font("Times New Roman", 12, FontStyle.Regular), true);
            PdfBrush brush = PdfBrushes.Black;
            PdfPen pen = new PdfPen(brush, 1.0f);

            // Create a PdfPageNumberField object and a PdfPageCountField object
            PdfPageNumberField pageNumberField = new PdfPageNumberField();
            PdfPageCountField pageCountField = new PdfPageCountField();

            // Create a PdfCompositeField object to combine page count field and page number field in a single field
            PdfCompositeField compositeField = new PdfCompositeField(font, brush, "Page {0} of {1}", pageNumberField, pageCountField);


            // Iterate through the pages in the document
            for (int i = 0; i < doc.Pages.Count; i++)
            {

                // Get a specific page
                PdfPageBase page = doc.Pages[i];

                // Get the page size
                SizeF pageSize = doc.Pages[i].Size;

                // Draw a line at the specified position
                page.Canvas.DrawLine(pen, 72, pageSize.Height - 50, pageSize.Width - 72, pageSize.Height - 50);

                // Measure the size the "Page X of Y"
                SizeF pageNumberSize = font.MeasureString(string.Format("Page {0} of {1}", i + 1, doc.Pages.Count));

                // Set the location of the composite field
                compositeField.Location = new PointF((pageSize.Width - pageNumberSize.Width) / 2, pageSize.Height - 45);

                // Draw the composite field on the page
                compositeField.Draw(page.Canvas);

            }

            // Save to a different PDF file
            doc.SaveToFile("AddPageNumbersToCenter.pdf");

            // Dispose resources
            doc.Dispose();
        }
    }
}

using Spire.Pdf.AutomaticFields;
using Spire.Pdf.Graphics;
using Spire.Pdf;
using System.Drawing;
using Spire.Pdf.License;

namespace AddPageNumbersToRigthCorner
{
    class Program
    {
        static void Main(string[] args)
        {
            // Apply your license key
            LicenseProvider.SetLicenseKey("License Key");

            // Create a PdfDocument object
            PdfDocument doc = new PdfDocument();

            // Load a PDF file
            doc.LoadFromFile("C:\\Users\\Administrator\\Desktop\\Terms of service.pdf");

            // Create font, brush and pen, which determine the appearance of the page numbers to be added
            PdfTrueTypeFont font = new PdfTrueTypeFont(new Font("Times New Roman", 12, FontStyle.Regular), true);
            PdfBrush brush = PdfBrushes.Black;
            PdfPen pen = new PdfPen(brush, 1.0f);

            // Create a PdfPageNumberField object and a PdfPageCountField object
            PdfPageNumberField pageNumberField = new PdfPageNumberField();
            PdfPageCountField pageCountField = new PdfPageCountField();

            // Create a PdfCompositeField object to combine page count field and page number field in a single field
            PdfCompositeField compositeField = new PdfCompositeField(font, brush, "Page {0} of {1}", pageNumberField, pageCountField);


            // Iterate through the pages in the document
            for (int i = 0; i < doc.Pages.Count; i++)
            {

                // Get a specific page
                PdfPageBase page = doc.Pages[i];

                // Get the page size
                SizeF pageSize = doc.Pages[i].Size;

                // Draw a line at the specified position
                page.Canvas.DrawLine(pen, 72, pageSize.Height - 50, pageSize.Width - 72, pageSize.Height - 50);

                // Measure the size the "Page X of Y"
                SizeF pageNumberSize = font.MeasureString(string.Format("Page {0} of {1}", i + 1, doc.Pages.Count));

                // Set the location of the composite field
                compositeField.Location = new PointF(pageSize.Width - pageNumberSize.Width - 72, pageSize.Height - 45);

                // Draw the composite field on the page
                compositeField.Draw(page.Canvas);

            }

            // Save to a different PDF file
            doc.SaveToFile("AddPageNumbersToRigthCorner.pdf");

            // Dispose resources
            doc.Dispose();
        }
    }
}