While using the customization wizard, if you have Acrobat DC Volume serial, you will have to input the serial number in Wizard and press button - Grant Offline Exception & Disable Registration
Note: This will only work if you have Acrobat DC Volume serial and not CCE (Creative Cloud Enterprise) Serial.
After creating the MST through wizard, install (or Deploy) the package using Setup.exe. This will ensure the MST Transform is applied through installation and on launch user will not see Sign In dialog.
If you are Creative Cloud Enterprise (CCE) customer, you will have to use CCP (Creative Cloud Packager) to deploy with registration suppressed enabled in CCP. Generic steps for this are:
1) Create the install package through CCP with registration suppress
2) Use DC Wizard to apply customization in DC installer
3) Install (or Deploy) Acrobat using Setup.exe. This will ensure your transform will be applied. (Do not deploy using exception deployer tool)
4) Run CCP Msi for registration suppression
5) If required for deploying other exception applications, run the Exception Deployer Application.
More information here - Creative Cloud Help | Deploying Adobe Acrobat
Thanks,
Karan