IndesignServer CS5.5 source

Tema2903, if the installation files are still available, then they will be located at https://licensing.adobe.com/.  You will need to make sure an log into an account that has access to the files.  The required information was provided as part of your organization's purchase.  

It is no longer possible to provide access to the files if your organization is unable to log in with the accounts assigned to download the software.

Adobe no longer supports CS5.5 so this link may not work for you

https://community.adobe.com/t5/Get-Started/Can-I-download-my-older-apps/td-p/10689585

You need to keep and archive safely your original install for all products, but most especially server products.