Pages doc resizes randomly

Ever since the most recent update of Pages, many times while I am viewing and editing a document I will somehow brush the mousepad accidentally and suddenly the document resizes.....and I can't seem to get it to go back to where it was before I did that.

Is there some new thing I am somehow triggering, is there a way to turn that off?

Its annoying more than anything else, but its a new thing and I would like it to stop now.