Illustrator has been saving some of my large files as PDFs rather than Illustrator files (when I am just pressing Cmd+S) and the file is definitely not a PDF to begin with. This is frustrating because anything outside of the artboard is no longer in the file, the file must be opened as individual artworks, and all of the text is saved as individual letters in cases where text is typed along a path, or it's saved as individual words.