It’s really easy to take lots of PDFs and make them into one PDF on a Mac, no special software necessary. 

This works in macOS 12 Monterey and in macOS 13 Ventura.

I put all the PDFs I want to merge into one folder, to make it easier. Open that folder and select all the files.  (If you want them in a specific order, make sure they’re in that order in the folder before you select them.)

Once they’re all selected, hold the “control” button and then click again. You’ll get a pop-up menu.

Select “Quick Actions” and then “Create PDF.”

It will create a PDF in the folder, and it automatically gives that file a name similar to the first file in your selection (usually the same name with a “2” added at the end). At that point you can easily rename that file to anything you want.