Currently, there is no way to change the URL of document that you have already uploaded on Issuu.
If you want a new document URL, you have to change the file name of the content on your computer, upload the content as a new document on Issuu and then delete the old content with the old URL from your Issuu account (if you want to).
NOTE: Deleting content will also delete statistics of the content.
After uploading the document on Issuu, the document name, that displays in the document URL is same as the document name on your computer. Therefore, before uploading content on Issuu, make sure that the title of your content is how you would like to appear in the Issuu URL.
If you are looking to change the title and description that is displayed below your content on Issuu, please see article for more information: Editing Your Document Title and Description.
If you are looking to change your Issuu account username/URL, please see article for more information: Changing Account Username.