Brian,
I don't really see any other ways, as it requires job concatenation. Even then, it wouldn't necessarely be something simple to setup either, because of the challenge of combining two different data streams.
Using the PDF Emulation might not be the simplest way to make it work. What I'd do would be to have a first process capture the first file, and send it to a folder.
Then, a second process would be triggered by this file using a Folder Capture, it would first have a branch to put the pdf into a folder, and then would move on to an Input action to capture the second pdf. Then, another branch would send that pdf to the same folder as the first one, under the same name, with the option to concatenate files checked. This way, this will create a two pages pdf. And after than branch, it will go to either a printer queue or Image output(or anything else you want), and call your form.
The form will use PDF Emulation, and will be a simple one page form with duplexing enabled. It will print the two pages of the concatenated pdf, front and back.
Hope this helps. Let me know if you have questions.
Regards,
Rapha