Adobe Illustrator is arguably the most popular and most powerful vector graphics software. If you ever work with a designer, it is very likely that you will have to deal with .ai files. Even if your final files must be in a different format (PNG, JPEG or something else), it would be nice to have vector sources in addition to them – it will make your life much easier if you need to change something and cannot hire the same designer again.
But how do you open an .ai file, if you don’t have Adobe Illustrator – which is a complex and expensive piece of software hardly used by anyone except professional designers? In most cases it’s really easy — you need only free Adobe Reader software, which is already installed on most computers. Right-click the .ai file you need to view, point to Open With… and then click Choose Program and choose Adobe Reader from the list. Or you may simply change the .ai extension to .pdf and open the file by double-clicking it.
This method works not only with Adobe Reader, but with any other software that can view or import .pdf files.
In some rare cases Adobe Reader won’t open an .ai file. Most likely, this is due to the fact that the designer cleared the Create PDF Compatible File checkbox in the Illustrator Options dialog (this option is on by default). This is really bad news, since you’re unlikely to open this file in any other program besides Adobe Illustrator. So, in this case you need to ask the designer to re-save the file with this option enabled.
And if you need a free alternative to Adobe Illustrator, I can recommend you Inkscape. This free open-source vector editing software is still in early stages of its development (the current stable version is 0.48), but its list of features is already comparable to Adobe Illustrator. Inkscape can import PDF-compatible .ai files and export graphics to .pdf.