Most probably, before making the purchase you have used the free trial to see how it works. If so, all you have to do is register your purchased key (provided by email by our reseller) by clicking on the green key in the PaperScan menu.
If you didn't download a trial, just go to either our general downloads page or to the dedicated page of the PaperScan Edition you own and click "Download Trial". Then enter the key as described above.
All you have to do is make the download by clicking the "Download" button on the dedicated page of the Edition you own. PaperScan will remember your commercial key, so you will not have to re-enter it again for registration even if uninstalling your existing version will be required before installing the latest one.
But the easiest way to download the latest version is to wait for the pop-up that announces each new release to appear on your screen when you open the software! Please note that you can disable this automatic update message.