Can I download measured data from an SD memory card to a PC over the network with SMARTDAC+ GX/GP series?

Yes. You can access the main unit via FTP, output a list of files and folders on the unit's external memory medium (SD memory card), and transfer, delete, or perform other operations on those files.
*For access from a web browser, enter "ftp://hostname.domainname/" in the URL box.

For details, see the user's manual (IM 04L51B01-01EN)
◊3.3 "Accessing the Measurement Data File on the GX/GP from a PC (FTP Server Function)."
User's Manual (IM 04L51B01-01EN)