Hi  Sumeet,
Check this example. Now please take its reference and correct your code.
Namespaces
C#
using System.Data;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;
VB.Net
Imports System.Data
Imports System.IO
Imports iTextSharp.text
Imports iTextSharp.text.pdf
Code
C#
protected void Export(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[3] { new DataColumn("Id", typeof(int)),
                        new DataColumn("Name", typeof(string)),
                        new DataColumn("Country",typeof(string)) });
    dt.Rows.Add(1, "John Hammond", "United States");
    dt.Rows.Add(2, "Mudassar Khan", "India");
    dt.Rows.Add(3, "Suzanne Mathews", "France");
    dt.Rows.Add(4, "Robert Schidner", "Russia");
    ExportToPdf(dt);
}
public void ExportToPdf(DataTable myDataTable)
{
    DataTable dt = myDataTable;
    Document pdfDoc = new Document(PageSize.A4.Rotate(), 10, 10, 10, 10);
    Font font13 = FontFactory.GetFont("ARIAL", 13);
    Font font18 = FontFactory.GetFont("ARIAL", 18);
    try
    {
        PdfWriter writer = PdfWriter.GetInstance(pdfDoc, System.Web.HttpContext.Current.Response.OutputStream);
        pdfDoc.Open();
        if (dt.Rows.Count > 0)
        {
            PdfPTable PdfTable = new PdfPTable(1);
            PdfTable.TotalWidth = 200f;
            PdfTable.LockedWidth = true;
            PdfPCell PdfPCell = new PdfPCell(new Phrase(new Chunk("Employee Details", font18)));
            PdfPCell.Border = Rectangle.NO_BORDER;
            PdfTable.AddCell(PdfPCell);
            DrawLine(writer, 25f, pdfDoc.Top - 30f, pdfDoc.PageSize.Width - 25f, pdfDoc.Top - 30f, new BaseColor(System.Drawing.Color.Red));
            pdfDoc.Add(PdfTable);
            PdfTable = new PdfPTable(dt.Columns.Count);
            PdfTable.SpacingBefore = 20f;
            for (int columns = 0; columns <= dt.Columns.Count - 1; columns++)
            {
                PdfPCell = new PdfPCell(new Phrase(new Chunk(dt.Columns[columns].ColumnName, font18)));
                PdfTable.AddCell(PdfPCell);
            }
            for (int rows = 0; rows <= dt.Rows.Count - 1; rows++)
            {
                for (int column = 0; column <= dt.Columns.Count - 1; column++)
                {
                    PdfPCell = new PdfPCell(new Phrase(new Chunk(dt.Rows[rows][column].ToString(), font13)));
                    PdfTable.AddCell(PdfPCell);
                }
            }
            pdfDoc.Add(PdfTable);
        }
        pdfDoc.Close();
        Response.ContentType = "application/pdf";
        Response.AddHeader("content-disposition", "attachment; filename=dsejReport_" + DateTime.Now.Date.Day.ToString() + DateTime.Now.Date.Month.ToString() + DateTime.Now.Date.Year.ToString() + DateTime.Now.Date.Hour.ToString() + DateTime.Now.Date.Minute.ToString() + DateTime.Now.Date.Second.ToString() + DateTime.Now.Date.Millisecond.ToString() + ".pdf");
        System.Web.HttpContext.Current.Response.Write(pdfDoc);
        Response.Flush();
        Response.End();
    }
    catch (DocumentException de)
    {
    }
    // System.Web.HttpContext.Current.Response.Write(de.Message)
    catch (IOException ioEx)
    {
    }
    // System.Web.HttpContext.Current.Response.Write(ioEx.Message)
    catch (Exception ex)
    {
    }
}
private static void DrawLine(PdfWriter writer, float x1, float y1, float x2, float y2, BaseColor color)
{
    PdfContentByte contentByte = writer.DirectContent;
    contentByte.SetColorStroke(color);
    contentByte.MoveTo(x1, y1);
    contentByte.LineTo(x2, y2);
    contentByte.Stroke();
}
VB.Net
Protected Sub Export(ByVal sender As Object, ByVal e As EventArgs)
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn(2) {
                        New DataColumn("Id", GetType(Integer)),
                        New DataColumn("Name", GetType(String)),
                        New DataColumn("Country", GetType(String))})
    dt.Rows.Add(1, "John Hammond", "United States")
    dt.Rows.Add(2, "Mudassar Khan", "India")
    dt.Rows.Add(3, "Suzanne Mathews", "France")
    dt.Rows.Add(4, "Robert Schidner", "Russia")
    ExportToPdf(dt)
End Sub
Public Sub ExportToPdf(ByVal myDataTable As DataTable)
    Dim dt As DataTable = myDataTable
    Dim pdfDoc As Document = New Document(PageSize.A4.Rotate(), 10, 10, 10, 10)
    Dim font13 As Font = FontFactory.GetFont("ARIAL", 13)
    Dim font18 As Font = FontFactory.GetFont("ARIAL", 18)
    Try
        Dim writer As PdfWriter = PdfWriter.GetInstance(pdfDoc, System.Web.HttpContext.Current.Response.OutputStream)
        pdfDoc.Open()
        If dt.Rows.Count > 0 Then
            Dim PdfTable As PdfPTable = New PdfPTable(1)
            PdfTable.TotalWidth = 200.0F
            PdfTable.LockedWidth = True
            Dim PdfPCell As PdfPCell = New PdfPCell(New Phrase(New Chunk("Employee Details", font18)))
            PdfPCell.Border = Rectangle.NO_BORDER
            PdfTable.AddCell(PdfPCell)
            DrawLine(writer, 25.0F, pdfDoc.Top - 30.0F, pdfDoc.PageSize.Width - 25.0F, pdfDoc.Top - 30.0F, New BaseColor(System.Drawing.Color.Red))
            pdfDoc.Add(PdfTable)
            PdfTable = New PdfPTable(dt.Columns.Count)
            PdfTable.SpacingBefore = 20.0F
            For columns As Integer = 0 To dt.Columns.Count - 1
                PdfPCell = New PdfPCell(New Phrase(New Chunk(dt.Columns(columns).ColumnName, font18)))
                PdfTable.AddCell(PdfPCell)
            Next
            For rows As Integer = 0 To dt.Rows.Count - 1
                For column As Integer = 0 To dt.Columns.Count - 1
                    PdfPCell = New PdfPCell(New Phrase(New Chunk(dt.Rows(rows)(column).ToString(), font13)))
                    PdfTable.AddCell(PdfPCell)
                Next
            Next
            pdfDoc.Add(PdfTable)
        End If
        pdfDoc.Close()
        Response.ContentType = "application/pdf"
        Response.AddHeader("content-disposition", "attachment; filename=dsejReport_" & DateTime.Now.Date.Day.ToString() + DateTime.Now.Date.Month.ToString() + DateTime.Now.Date.Year.ToString() + DateTime.Now.Date.Hour.ToString() + DateTime.Now.Date.Minute.ToString() + DateTime.Now.Date.Second.ToString() + DateTime.Now.Date.Millisecond.ToString() & ".pdf")
        System.Web.HttpContext.Current.Response.Write(pdfDoc)
        Response.Flush()
        Response.End()
    Catch de As DocumentException
    Catch ioEx As IOException
    Catch ex As Exception
    End Try
End Sub
Private Shared Sub DrawLine(ByVal writer As PdfWriter, ByVal x1 As Single, ByVal y1 As Single, ByVal x2 As Single, ByVal y2 As Single, ByVal color As BaseColor)
    Dim contentByte As PdfContentByte = writer.DirectContent
    contentByte.SetColorStroke(color)
    contentByte.MoveTo(x1, y1)
    contentByte.LineTo(x2, y2)
    contentByte.Stroke()
End Sub
Screenshot

For more details refer below article.