Sheet Fill Direction, Merge to Columns instead of Rows
Avery Design & Print Online defaults to filling sheets across the rows of labels. If you prefer to fill the sheet by columns instead, to change the fill direction of your labels:
Navigate to Step 4 Preview and Print.
Select Print It Yourself, if this is an option.
In the Preview and Print Options choose Show Print Options
Then, from Fill Direction choose: Fill Across or Fill Down