You have a lot of pages, I would be looking to do something that is easily replicated.

If the background is pastel blue on all pages, I would make a simple rectangle in the same colour.
Make it, say, 100px wide and tall enough to reach the bottom of your longest page (this ensures the arrow does disappear once you've scrolled past the trigger).
Place the top of the rectangle where you want the arrow to appear and make a note of the x/y coordinates, so you can locate it easily. (the example is set to x:0, y:1200)
Name it 'trigger1' (or whatever).
Send it to the back of the page.
Arrange > Repeating Object > Repeat on all pages

Your arrow should, indeed, be on the MouseOff layer. Create it as the first set of instructions and make it repeat as above.

>>> Sue Arrow Long.xar <<<