I need to merge or un-split multiple PDFs back to a single large format single page print

To elaborate on Bernd's suggestion, in Photoshop, File> Automate> Photomerge. This works very well with images where Photoshop can determine where to overlap, but I tried it with the first 16 pages of your pdf and it was not able to stitch them together, it might work with a lot of tweaking, but it would be faster to use InDesign. Create a large InDesign page and place the 16 pages into it, moving and cropping until the design is whole again, then export to a new pdf.

With Photoshop you can stitch the pages.

You can print them out using the Multiple option to a new PDF file, but they will have large gaps between them. To avoid that you would need to first crop all the white space around them and then merge them using a custom-made script.