Have a question here. In the upper right portion here I have a Finder window open with a .PDF file selected. I am trying to drag and drop it into the iCloud Pages window I have open at the lower right. But when I drag and drop, it snaps right back. The same file but as a .Pages format dropped right into place. What am I misunderstanding? Are PDF formats incompatible with Pages folders? Are there any other incompatibilities? For instance, what can I and what can't I drop into a Numbers folder?