Did you know this trick?  You can simply change the extension of an Adobe Illustrator® file (recent versions) from .ai to .pdf and you’ll be able to open the file into any PDF viewer such as Qoppa’s cross-platform PDF editor PDF Studio. Why is that so?

Because in recent versions, ai files are saved by saving a PDF file and embedding in it the PGF (Progressive Graphics Format) which is the file format used by Adobe Illustrator for editing purposes.

So simply put, an ai file is a valid PDF file with additional information for editing.

This explains why files saved with the ai file extension in Adobe Illustrator will be bigger than when those saved with the pdf file extension, the more compact version for viewing.In summary for PDF Studio users: Opening an ai file in PDF Studio for viewing, yes you can! But you will not be able to edit the graphics in the same way you would in Adobe Illustrator of course!