http://www.youtube.com/watch?v=a59LvC6BOuk
Use the above link
private void btnopen_Click(object sender, EventArgs e){
OpenFileDialog openFileDialog1 = new OpenFileDialog();
if (openFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK){
axAcroPDF1.src = openFileDialog1.FileName;
}
}