When DropDMG installs and App, the user has to click and drag the .app to the Applications folder.
However, just before then, during the installation process, after the user accepts the license agreement, I want to copy some files my .app will need to the User’s Documents folder.
Disk images don’t run any code, so you would either need to drag and drop or put an installer instead of a .app on the .dmg. In your case, it sounds like the standard approach would be to put the files inside of your .app package and have the app itself copy them to the right place the first time it’s launched.