When you are sending an Illustrator file to the printers it is usually best to convert the fonts to outlines. This means that even if the person you are sending the file does not have the fonts you have used installed they will still be able to print it. When you convert fonts to outlines, the program will look at the fonts as images rather than text thus fixing any upload errors that result when fonts are not embedded in your file.
Here is how to convert fonts to outlines in Adobe Illustrator
Select all text.
Click Type Menu> Type> Create Outlines
Text now has a blue outline.
Save a copy and re-upload.