Hello,
Yes, as mentioned by odsven, we recommend installing the Web Interface in the DMZ if it is exposed to the Internet. See section Installing Web Interface and Administration Console in DMZ in our Installation Notes.
Also, if you want to have more security for a Web Interface available from the Internet, you can enable SSL for it. Since Adaxes Web Interface is an IIS application, you can enable SSL the same as you do for any other IIS web application. For example, have a look at this walkthrough by Microsoft.