can the installation unid or HD be changed?

Hi there

Hope you are doing well and thanks for reaching out.

The Installation ID (UNID) or Hardware ID (HD) used by Adobe Acrobat Reader is automatically generated and tied to your system configuration. These identifiers help with internal tracking and functionality, but they cannot be manually changed or reassigned.

You can also try Uninstalling and then reinstalling the app  to another drive to free up some space on HD c:

For self-help and future reference, please check the help page: https://helpx.adobe.com/acrobat/get-started.html

Hope this information will help.