[jusmee]

Take a look at Microsoft Lens/Office Lens. I think there are versions for Android, Windows and Apple. I know for sure the Android version can export photos as a pdf.

Thanks, yes, I haven't looked at the software side yet, but yes, I remember there are apps that can do it automatically.  I will use one of them probably.

That still leaves the question of the image quality required.  I don't know much about document archival, but I am assuming that you need at least as much resolution as the typical printer will print.