How To Customize Subscription Preview Template
Summary: In Subscription Management, when you open a subscription and you look at it in the Summary - Overview page, you can use the Actions menu and select Preview. This preview creates a printable PDF output that you can use to preview the subscription.
As per documentation Using Oracle BI Publisher, you can create custom layout templates by adding the subscription data model attributes supplied with the application. (By default, there's only one template supplied: Subscription template.)
Have found that the Subscription Preview template exists here in catalog but there is no way to copy and paste it here. How to create a new template layout and associate it on the Subscription.