zdnet[.]com/article/how-to-combine-pdfs-on-both-windows-and-mac-easily-and-securely/
...to combine several PDFs on both Windows and Mac, you can go to adobe.com and click on PDF & E-signatures, then select Online Tools: Work with PDFs nowAdobe will allow you to combine and download PDFs once without an account, but subsequent downloads will require you to sign in, so you can create a free account or sign in on the next step
When you sign in with an Adobe ID, you also have access to two free premium transactions every 30 days, so you're unfortunately limited to being able to combine PDFs only twice in a month.
