I just updated Illustrator CC yesterday, and have been having an issue ever since. I have a multi-artboard Illustrator file (images, text, etc.) that I am trying to save as a PDF proof that I can email. When saving as the Illustrator Default preset, it works fine. However, when I try to save as "smallest file size" preset, I receive an unknown error when saving. I have to save the file so that it is as small as possible. I have tried creating a custom preset with custom settings, but that encounters the same issue. I have also tried reverting to an older version of Illustrator and still encounter the issue.
I have researched this and tried renaming the Adobe PDF Settings folder, but that has not solved the problem. No error information is provided other than a pop-up that says "unknown error". Can someone please help? This is a time sensitive project and I cannot share with my team.