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

        //MemoryStream ms = new MemoryStream();
        pageImage.Image?.Dispose();
        drawingBitmap.Save("C:\\test.png"); //pageImage.ImageLocation);

        
    }
}

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

        //MemoryStream ms = new MemoryStream();
        pageImage.Image?.Dispose();
        drawingBitmap.Save("C:\\test.png"); //pageImage.ImageLocation);

        
    }
}

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;

        pageImage.Invalidate();
    }
}

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

        drawingBitmap.Save(pageImage.ImageLocation);
    }
}

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;

        pageImage.Invalidate();
    }
}

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

        drawingBitmap.Save(pageImage.ImageLocation);
    }
}

drawingBitmap = new Bitmap(pageImage.ImageLocation);
//g = pageImage.CreateGraphics();
g = Graphics.FromImage(drawingBitmap);
pageImage.Image = drawingBitmap;

drawingBitmap = new Bitmap(pageImage.ImageLocation);
//g = pageImage.CreateGraphics();
g = Graphics.FromImage(drawingBitmap);
pageImage.Image = drawingBitmap;