All I needed to do was to chop off the last page of a PDF and insert a one page PDF in front of it.
I did a little searching and found a number of online free PDF editors, but I didn't want to submit my data over the Internet to some third party I'm not familiar with. I wanted a downloadable, installable simple PDF editor.
TechRadar's 5th suggestion was just the thing:
The best free PDF editors to use in 2021 | TechRadar
They pointed to the PDFsam web site:
Features in PDFsam Basic, free and open source - PDFsam
The page there says, "PDFsam Basic, a free, open source, multi-platform software designed to split, merge, extract pages, mix and rotate PDF files."
Open source was the icing on the cake. Someone developed a useful tool and anyone can look at the source code.
The program did exactly what I wanted. I merged the two PDFs with the short one first and then I split the PDF to drop the last page. Perfect.
One thing to note, the default setup has a checked box to install a trial of PDFsam Enhanced. Just uncheck that box if your needs are basic like mine are.