Check this post : https://blogs.sap.com/2019/09/25/how-to-merge-multiple-pdf-forms-into-single-one-and-write-in-application-server/
In SM37, type JDBG (like Job Debug in Background).
Read MoreIn transaction where you can edit code (like SE38, SE80…) :
Refer to the links below :
Building Your First BADI
How to Implement a BADI
How to use filter in a BADI