About this tool
Illustrator .ai files saved with the "Create PDF Compatible File" option (turned on by default) include a full PDF view of the design. This viewer reads that view right on your device, so you can review a design even if you don't have Illustrator, Photoshop or Acrobat.
It's useful for reviewing logos, packaging, flyers and final artwork that a designer sends you, or for checking a PDF quickly from your phone.
It's a read-only viewer: it doesn't edit the file. If your .ai was saved without PDF compatibility, or it's from a very old version of Illustrator, it can't be displayed; ask whoever created it to save it again with that option.