Compile multiple documents into a single pdf

Hi,

Is it possible to compile multiple pdfs into one?

I have an invoice which is created then saved in my database then, I also have an appendix which is also saved when I generate my invoice. These are 2 different pdf documents.

I would like these 2 documents to be generated on a single pdf in this order: 1-invoice, 2-annex

Is it possible to combine the 2 documents into a single pdf?

Thanks for your help.