The download can do most things but it cannot save unless you buy it.
Download PC version
Download Mac version
WriteItNow runs on PCs (Windows 7, 8 and 10) and Macs (OS X)
if the free demo runs on your computer the full version will as well.
Download WriteItNow 4 here
Try the free demo first. If you like it buy codes to convert it to the full version.