Alignment of cells in itextsharp

I have a problem and I can not find a solution, I'm using itextesharp in a windowsfroms application, I've created a table with 7 cells and I would like to align some right and others centered. unfortunately I can only align all the cells to the right or the left. through the table.DefaultCell.HorizontalAlignment = 0; I'll post the code. Thank you in advance for your help.

            PdfPTable tabela = new PdfPTable(7);
            PdfPCell celula = new PdfPCell();
            tabela.TotalWidth = 790f;
            //  celula.HorizontalAlignment = 1;
            tabela.DefaultCell.HorizontalAlignment = 0;
            tabela.LockedWidth = true;
            float[] widths = new float[] { 16F, 40f,45F,60F,15f, 15f, 15f };
            tabela.SetWidths(widths);
            tabela.HorizontalAlignment = 0;
            celula.HorizontalAlignment = 0;
            strSql= "  ";
            con = new SqlConnection(strcon);
            SqlCommand cmd2 = new SqlCommand(strSql, con);
            cmd2.Parameters.AddWithValue("@DataI", DateTime.Parse(mtbDtInicial.Text));
            cmd2.Parameters.AddWithValue("@DataF", DateTime.Parse(mtbDtFinal.Text));
            cmd2.Parameters.AddWithValue("@ifd", emn1);
            con.Open();
            SqlDataReader ler = cmd2.ExecuteReader();
            while (ler.Read())
            {
                tabela.AddCell (ler[4].ToString()); //conta a direita
                tabela.AddCell(ler[0].ToString());//título  a direita
                tabela.AddCell(ler[1].ToString());//subtitulo a direita
                tabela.AddCell(ler[2].ToString());//descr a direita
                tabela.AddCell(ler[6].ToString());//valor centralizado
                tabela.AddCell(ler[7].ToString());//perce centralizado
                tabela.AddCell(ler[8].ToString());//desp centralizado
            }
            document2.Add(tabela);