How to Open Adobe Illustrator Files if you don have Adobe Illustrator?
If you only need to preview the file you can can change the file extension from .ai to .pdf. To do that all you need to do is rename the file so that it ends with .pdf instead of .ai. Once you change the extension it will change the file type and you can open the PDF in a software like Adobe Reader. If you need to edit the file you could download a free software such as Inkscape (https://inkscape.org/en/download/and it till) that will let you edit the file or download a trial version of Adobe Illustrator.