Managing PDF data with Excel

This seems like an Adobe issue not an Excel issue, not sure you will find much help here regarding that. My guess would be it follows some order according to the fields order (some numbering/order determined by Adobe when the fields are created and/or a property of the fields). If its an exposed property you may be able to adjust it for each field to the order you like, if not you may have to shuffle the columns after as you see fit and/or resign the form to follow your desired order.

Set Tab Order to Order Tabs Manually (or any other) and test it
but this is not Excel problem

You can order fields based on the structure, rows, or columns. For most forms, click Tab Order and choose Order Tabs by Structure as Acrobat X does a good job of ordering for you.
If you want to change the order manually, click and drag the field in the Fields pane. You'll see the field's number change on the page.

or

from the left side select Order
order1.jpg

then drag and drop to set order as you wish. It doesn't change place of fields in your file but change priority only to exapoert in choosen order
order2.jpg