I have two sites in one site collection with respective document libraries. Is there a way to automatically copy files by creation from one library to the other sites library and the other way around? In the end there should be 2 libraries with the exact same content. I do only have OOTB functions and SharePoint Designer available, is there a possible way to solve this?
Using SharePoint Designer workflow you cannot copy documents to library in different site. You may have to create custom workflow using visual studio.
You can check the link below of similar issue.