Combine attached PDF with master PDF to make a single PDF

You need to open all attachments first.

Each will open on its oen separate tab.

When you use the combine tool method as suggested by Berndt Alheit, you'll get an option that says combine from opened files.

This will get all these files combined together in addition to the master PDF document.

The combine files tools will commit to an irreversible file selection. If you only want to combine the file attachments into one PDF, close the tab where the master PDF is opened, then use the combine files tool.

The sequence of ateps offered by this wizard is very straight forward, intuitive, and visually easy to understand.

That said, you will also get an option to delete the source files once they're merged into one PDF, or keep them.

I'm not sure about the exactl workflow for getting the Acrobat Combine files to use file attachments. If you open the attachment and then select Add Open PDFs on Combine Files, the attachment does not appear for selection. So not sure if this works. @Bernd Alheit Can you be more specific about how this works?

However, I do know that it is possible to write a script that opens all the attachement and copies pages into the parent file. 

Use combine files with the master file.

It will work when the file is a portfolio.