On the last window you can select by mouse (Press and hold down the CTRL key while you click images) which images you need to be saved...
![Scanitto Lite to single PDF prepare](/images/single-pdf1.png)
... and than click "Save to single PDF" button on the toolbar.
![Save to single PDF](/images/single-pdf.png)
Scanitto Lite will ask you where you wish PDF to be saved.