The URL link is created using the account name (in this sample, it is Admin-Walkthrough) and the edition title (in this sample, it is Test).
When you change the URL, you are changing the edition title. What is static is the Account Name, as that is part of the URL.
To change the URL, simply edit the edition title or upload a new PDF into the same template to keep the same settings but give the content a new edition title. In the sample below, we have changed the URL from "Test" to "Test2":
You can see that the account name is the same (Admin-Walkthrough) but the edition title has changed, thus changing the name of the URL.
Once you follow these steps, the URL will be changed. Now you have changed the URL.