Here's a script for generating PDF output but appending it as a new page to an existing PDF file.

To install, put the AddPageToPDF.js script file into the MoI appdata commands folder
(more info: MoI FAQ how to install plugin script)

Make a new "tools" sub-folder inside the MoI appdata folder and unzip one of podofomerge_win.zip or podofomerge_mac.zip into there.

If you're on Mac you probably need to go to a Terminal window and run this to clear the quarantine flag:
sudo xattr -cr podofomerge

Then when you run the new AddPageToPDF you should be able to pick an existing PDF file and it should output a new page in it.

- Michael

Edit: Updated AddPageToPDF.js script to run on v4 Mac.