private bool isDrawing = false;
private Point pos;
private Pen drawingPen;


private void PageImage_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left) 
    {
        isDrawing = true;
        pos.X = e.X;
        pos.Y = e.Y;
    }
}

private void PageImage_MouseDrawMove(object sender, MouseEventArgs e)
{
    if (isDrawing)
    {
        g.DrawLine(drawingPen, pos, e.Location);

        pos = e.Location;
    }
}

private void PageImage_MouseUp(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        isDrawing = false;


        Bitmap bitmap = new Bitmap(pageImage.Image);
        bitmap.Save(pageImage.ImageLocation);
    }
}

private bool isDrawing = false;
private Point pos;
private Pen drawingPen;


private void PageImage_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left) 
    {
        isDrawing = true;
        pos.X = e.X;
        pos.Y = e.Y;
    }
}

private void PageImage_MouseDrawMove(object sender, MouseEventArgs e)
{
    if (isDrawing)
    {
        g.DrawLine(drawingPen, pos, e.Location);

        pos = e.Location;
    }
}

private void PageImage_MouseUp(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        isDrawing = false;


        Bitmap bitmap = new Bitmap(pageImage.Image);
        bitmap.Save(pageImage.ImageLocation);
    }
}

g = pageImage.CreateGraphics();

g = pageImage.CreateGraphics();