After an item is created you can always change the order of the documents attached to it.

Go to the item screen for the subject meeting.

How do I edit an item?

The third tab is the Attachments tab

The Attachments tab has two parts: the list of documents currently attached to the item on the left, and a viewport on the right.

Grab any attachment the list of attachment on the left, drag it and drop it where you want it. The order is updated immediately upon dropping.