How to export datagriedview to PDF with UTF8

Hello. I want to export datagriedview to PDF with UTF8. When I export to PDF, header texts is shown with lack of letters. I am using Azerbaijani alphabet. We have letters like "ə, ı, ü, ö, ğ, ç, ş". Since I am beginner in C#, i don't know what to do. I please you to help me.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Reflection;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;

namespace Loan_Calculator
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        double kreditmeblegi;
        double illikfaiz;
        double fm;
        double value1;
        double ay;
        double il;
        double ayliqodenis;
        double umumiodenis;
        double esasborc;
        double faiz;
        double qaliqmebleg;
        double odenilenfaiz;
        int nomre;

        DataTable dt = new DataTable();

        private void button1_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(textBox1.Text) || string.IsNullOrEmpty(textBox2.Text) || string.IsNullOrEmpty(textBox3.Text))
            {
                MessageBox.Show("Rəqəmləri daxil edin.");
            }

            else
            {
                if (comboBox2.Text == "ay")
                {
                    kreditmeblegi = Convert.ToDouble(textBox1.Text);
                    illikfaiz = Convert.ToDouble(textBox2.Text);
                    ay = Convert.ToDouble(textBox3.Text);

                    fm = illikfaiz / (12 * 100);

                    value1 = 1 - (1 / Math.Pow((1 + fm), ay));

                    ayliqodenis = (kreditmeblegi * fm) / value1;
                    umumiodenis = ayliqodenis * ay;
                    odenilenfaiz = umumiodenis - kreditmeblegi;

                    DateTime date = this.dateTimePicker1.Value.Date;
                    DateTime nyear = new DateTime();
                    string format = "dd / MM / yyyy";

                    qaliqmebleg = kreditmeblegi;

                    for (int i = 1; i <= ay; i++)
                    {
                        nomre = nomre + 1;
                        nyear = date.AddMonths(i);
                        faiz = qaliqmebleg * fm;
                        esasborc = ayliqodenis - faiz;
                        qaliqmebleg = qaliqmebleg - esasborc;

                        int n = dataGridView1.Rows.Add();
                        dataGridView1.Rows[n].Cells[0].Value = nomre.ToString();
                        dataGridView1.Rows[n].Cells[1].Value = nyear.ToString(format);
                        dataGridView1.Rows[n].Cells[2].Value = ayliqodenis.ToString("N2");
                        dataGridView1.Rows[n].Cells[3].Value = esasborc.ToString("N2");
                        dataGridView1.Rows[n].Cells[4].Value = faiz.ToString("N2");
                        dataGridView1.Rows[n].Cells[5].Value = qaliqmebleg.ToString("N2");
                    }

                    button1.Enabled = false;
                }

                else
                {
                    kreditmeblegi = Convert.ToDouble(textBox1.Text);
                    illikfaiz = Convert.ToDouble(textBox2.Text);
                    il = Convert.ToDouble(textBox3.Text) * 12;

                    fm = illikfaiz / (12 * 100);

                    value1 = 1 - (1 / Math.Pow((1 + fm), il));

                    ayliqodenis = (kreditmeblegi * fm) / value1;
                    umumiodenis = ayliqodenis * il;
                    odenilenfaiz = umumiodenis - kreditmeblegi;

                    DateTime date = this.dateTimePicker1.Value.Date;
                    DateTime nyear = new DateTime();
                    string format = "dd / MM / yyyy";

                    qaliqmebleg = kreditmeblegi;

                    for (int j = 1; j <= il; j++)
                    {
                        nomre = nomre + 1;
                        nyear = date.AddMonths(j);
                        faiz = qaliqmebleg * fm;
                        esasborc = ayliqodenis - faiz;
                        qaliqmebleg = qaliqmebleg - esasborc;

                        int n = dataGridView1.Rows.Add();
                        dataGridView1.Rows[n].Cells[0].Value = nomre.ToString();
                        dataGridView1.Rows[n].Cells[1].Value = nyear.ToString(format);
                        dataGridView1.Rows[n].Cells[2].Value = ayliqodenis.ToString("N2");
                        dataGridView1.Rows[n].Cells[3].Value = esasborc.ToString("N2");
                        dataGridView1.Rows[n].Cells[4].Value = faiz.ToString("N2");
                        dataGridView1.Rows[n].Cells[5].Value = qaliqmebleg.ToString("N2");
                    }

                    button1.Enabled = false;
                }

                if (Convert.ToDouble(textBox1.Text) == 0 || Convert.ToDouble(textBox2.Text) == 0 || Convert.ToDouble(textBox3.Text) == 0)
                {
                    MessageBox.Show("Sıfır daxil etmək olmaz!");
                    button1.Enabled = true;
                }

                label9.Text = ayliqodenis.ToString("N2") + " " + comboBox1.Text;
                label10.Text = umumiodenis.ToString("N2") + " " + comboBox1.Text;
                label12.Text = odenilenfaiz.ToString("N2") + " " + comboBox1.Text;

            }
        }

        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
        (e.KeyChar != '.'))
            {
                e.Handled = true;
            }

            // only allow one decimal point
            if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
            {
                e.Handled = true;
            }
        }

        private void textBox2_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
        (e.KeyChar != '.'))
            {
                e.Handled = true;
            }

            // only allow one decimal point
            if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
            {
                e.Handled = true;
            }
        }

        private void textBox3_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
        (e.KeyChar != '.'))
            {
                e.Handled = true;
            }

            // only allow one decimal point
            if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
            {
                e.Handled = true;
            }
        }

        private void haqqındaToolStripMenuItem_Click(object sender, EventArgs e)
        {
            About about = new About();
            about.Show();
        }

        private void wiewHelpToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Help melumat = new Help();
            melumat.Show();
        }

        private void təmizləToolStripMenuItem_Click(object sender, EventArgs e)
        {
            textBox1.Clear();
            textBox2.Clear();
            textBox3.Clear();
            comboBox1.Text = "AZN";
            comboBox2.Text = "ay";
            dateTimePicker1.Value = DateTime.Now;
            label9.Text = "0";
            label10.Text = "0";
            label12.Text = "0";
            dataGridView1.Rows.Clear();
            nomre = 0;
            button1.Enabled = true;
        }

        private void çıxToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void comboBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            e.Handled = true;
        }

        private void comboBox2_KeyPress(object sender, KeyPressEventArgs e)
        {
            e.Handled = true;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void pDFəÇıxartToolStripMenuItem_Click(object sender, EventArgs e)
        {
            //Creating iTextSharp Table from the DataTable data
            PdfPTable pdfTable = new PdfPTable(dataGridView1.ColumnCount);
            pdfTable.DefaultCell.Padding = 2;
            pdfTable.WidthPercentage = 90;
            pdfTable.HorizontalAlignment = Element.ALIGN_CENTER;
            pdfTable.DefaultCell.BorderWidth = 1;

            //Adding Header row
            foreach (DataGridViewColumn column in dataGridView1.Columns)
            {
                PdfPCell cell = new PdfPCell(new Phrase(column.HeaderText));
                cell.BackgroundColor = new iTextSharp.text.Color(230, 230, 230);
                pdfTable.AddCell(cell);
            }

            //Adding DataRow
            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                foreach (DataGridViewCell celli in row.Cells)
                {
                    try
                    {
                        pdfTable.AddCell(celli.Value.ToString());
                    }
                    catch { }
                }
            }

            SaveFileDialog sfd = new SaveFileDialog();
            sfd.Filter = "Pdf File |*.pdf";
            if (sfd.ShowDialog() == DialogResult.OK)
            {
                Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 10f, 10f);
                PdfWriter wri = PdfWriter.GetInstance(pdfDoc, new FileStream(sfd.FileName, FileMode.Create));
                pdfDoc.Open();
                Paragraph paragraph = new Paragraph("Kreditin Hesablanması");
                paragraph.Alignment = Element.ALIGN_CENTER;
                pdfDoc.Add(paragraph);
                pdfDoc.Add(pdfTable);
                pdfDoc.Close();
                MessageBox.Show("Ödəniş cədvəli PDF-ə çıxarıldı.");
            }
        }
    }
}