From CreativePro.com –CreativePro Tip of the Week: Viewing Illustrator Artwork as Outlines:
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This CreativePro Tip of the Week for Viewing Illustrator Artwork as Outlines was sent to CreativeProse email subscribers on May 3, 2017. Sign up now and every week you'll get a new tip, plus roundups of new articles, and exclusive deals sent right to your Inbox! Just scroll down to the bottom of this page, enter your email address, and click Submit! We?ll take care of the rest. Now, on with the tip! If you’ve used Adobe illustrator for any amount of time, you know that you can view artwork in either Preview mode (where you see all strokes, fills, effects, etc) or Outline mode (where you see just vector paths). And you probably know the keyboard shortcut for toggling between modes, Command+Y (Mac) or Ctrl+Y (Windows). But you might not know that Illustrator also offers the flexibility to see individual layers, or just placed artwork in Preview mode, as well as the ability to see artwork in both modes simultaneously. To see a single layer in Preview or Outline mode, hold the Command key (Mac) or Ctrl key (Windows) and click the layer’s eye icon in the Layers panel. To see placed images in Outline mode, choose File > Document Setup, and select…”
