Here there are some propositions about how to merge PDF documents.
Tools to merge PDFs
There is a limit in Windows to print up to 16 files. If you need to print at the same time more than 16 files, do it in batches.
To merge PDFs, use open-source free tool PDFsam Basic.
During its installation ensure you uncheck a checkbox during installation that allows to install Enhanced version instead.
You can use PDF Merge & Splitter too. It is available from the Microsoft Store.
Default PDF app in Mac is Preview. It allows to edit and merge PDFs.
You can find more info on this link.
- Edward Mendelson; “How to combine PDF files“; PCMag.com