I have never changed the setting (Always) for opening PDFs in one window. However, suddenly PDFs are shown in different windows...Why is it like this and how can I solve this?
The behavior has changed in Monterey. To get a tabbed window with all open files, you need to select "Merge All Windows" from Preview > Window.
Oh, thanks. Should I do that every time I open a new pdf?
You're welcome. If you want the newly opened PDF in a Tab with the rest, yes.
Multiple PDFs in one window (several tabs): "Prefer open tabs when opening documents" to 'Always' failed
