Set tab order in Manage form fields panel
Click the Manage form fields panel in the Navigation Pane. Click Set Order button in the upper-left corner of the Manage form fields panel and choose to order tabs by row/column/structure. Check Show tab numbers to view the tab order.
You can also change the tab order by dragging and dropping a field to the desired place within the Manage form fields panel. You can only move one field at a time.
Set tab order in Page thumbnail panel
Click the Page thumbnails panel in in the Navigation Pane. Right-click the page where you need to change the tab order and choose Properties…. In the Page Properties dialog box, select one order in the Tab Order tab.
Set tab order manually with Select Annotation tool
With the Select Annotation tool selected, right-click a form field, and choose Set Tab Order. Click anywhere in the field that you want it to be the first in the tabbing order. The number in the upper left corner will be set as 1. Click each of the other fields in the order that you want tabbing to occur.
Note: You can only set tab order within one page.