Hi Jacob,
You can buy a subscription for captivate from Adobe.com. Select the Subscription option when you add the product to your online cart. You are given a serial number at the end of your purchase. Just copy and paste the serial number when you launch your trial and follow the onscreen instructions to start using your subscription product.
Please refer : http://www.adobe.com/uk/products/captivate/faq.html#subscription
To download captivate please navigate to : http://www.adobe.com/cfusion/tdrc/index.cfm?product=captivate&loc=en_u s