WordSmith Tools is obtained by downloading the whole program. You can download from this website.
What you get when you download is the complete package. It will run in demo mode if you have no registration code. In demo mode it does everything the full program does but will only show you a sample of the output.
2. Purchase a Registration Code
To convert from demo mode to full use, you purchase a registration code and then in the main menu in WordSmith, choose the "Update from Demo" option. The price for a single user is currently around £50 (approx. US$70 or €60); a licence for up to 10 users is five times the single price and for up to 50 users ten times the single user price. (Can't afford that? -- download a free registration for WordSmith 4.0 here)
You can purchase here.
If you own a previous version of WordSmith, you can apply for a 50% discount on the current version. Send us (firstname.lastname@example.org) details of your original purchase including the date, registration code, name and other details and get access to the 50% discount rate.