You can't, there are no devices that I know of that can do that.
JPG is not capable of multiple pages so it automatically does a file per page.
TIFF has 2 standards, single and multipage, so it can be made to do so.
PDF has no reason to do it so it doesn't, the email thing is to bypass SMTP server limitations, so if your email provider allows a 25MB attachment size, you set the printer to split it every 24-25MB and it will send a scan that would be 48MB into 2 files to allow transfer. But that scenario does not exist on Harddrives or FTP servers or SMB shares so it is not considered.
If you need single page pdf and only want to scan once, you could scan jpg, then run a converter to convert jpg to pdf.
Irfanview can do it with a free plugin.