As an IT administrator, there are a few steps you can take to prevent PDF files from being opened.
The first step is to block access to the PDF file. This can be done in a few different ways. The most common is to use a web filter or firewall to block access to the PDF file. This will prevent users from being able to access the PDF file, either via a web browser or other applications.
The second step is to use encryption. Encrypting the PDF file will make it impossible for users to open the file unless they have the encryption key. This will ensure that only authorized users are able to open the file.
The third step is to use digital rights management (DRM) software. DRM software will allow you to control who is able to access the PDF file and what they can do with it. This includes preventing the user from printing, copying, or modifying the file.
Finally, you can use a content delivery network (CDN). A CDN is a system of distributed servers that will store and deliver the PDF file for you. This will ensure that users are only able to access the PDF file from the CDN, making it much harder to download or open the file.
These four steps can help you prevent PDF files from being opened. However, it is important to remember that these measures are not foolproof. If a user is determined enough, they may be able to bypass the security measures you have put in place. As such, it is important to regularly audit your security measures and update them as needed.