I am trying to sync my library across my personal (MacOS) and work (Windows) devices. I add through DOI and then manually attach the file through a local copy. For some reason my MacOS device will automatically store any file as a linked copy and into an iCloud fold named 'Zotero attachments'. I have checked my settings>advanced>files and folders and I have no set linked attached directory and only have it set to default directory. How come my Zotero on the MacOS device is choosing to attach pdf files as links and not automictically place them in the default (/Users/Username/Zotero) as it has done with plenty of other files?

This is likely my naivety but it is becoming frustrating to work out!