Step and repeat the 1-up PDF file on the layout

From the View menu, select Step and Repeats.
From the View menu, select as Thumbnails, if you are in the list mode.
From the 1-Up Artwork pane, do one of the following actions:
- Drag the Vitamins.p1.pdf file to anywhere in the imported layout that appears on the Layouts pane
- Right-click Vitamins.p1.pdf and select Assign 1-up Artwork to Position

Space shortcuts