How big is the download size for the free demo of DRONE The Game?

From the game's Steam Page, you can see under System Requirements just how much space is needed by the game:

Keep in mind that 14GB is the final size needed for the game, but the actual download that Steam performs may be smaller, since game files are compressed and unpacked after download.

For the Demo, if you click on the Download Demo button, you will see a prompt that tells you how big the Demo is (~3.5GB):