If you're looking to add slides above what is available in Valve, we'd recommend downloading the PDF report from Valve and converting it to a Powerpoint (we use https://smallpdf.com/pdf-to-ppt).
By doing so, you are able to edit everything and/or add slides as needed. When you're in the PDF builder, after clicking Generate Report, there's a button called Visibility Settings where you can toggle off page numbering. If you're planning to add in slides, we'd recommend doing so, it'll save you a good chunk of time later and ensure things are clear for your client.