Strange document appeared in Pages

I opened my MacBook Air at work last Saturday. There was a document open in Pages which I had never seen before. It appears to be a text version of a children's book.

I have no idea where it came from. It is stored in my iCloud Drive - Pages folder and info says it was created and last modified at the moment I opened my MacBook.

Is there any way I can find out where this came from? it doesn't appear in my downloads folder, and I have no memory of this document before I saw it.

Any ideas?