I think these might be guides in your layout. The page layout help talks about them a bit. Try right clicking on the ruler on the left side of your layout and selecting Clear All Guides. Not positive, but would be worth a try. I had these mystery lines show up today and this was what it was, clicking View>Guides will hide them quickly. Dropped something on my keyboard, so there must be a hotkey or func key that turned them on. Thanks!
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