Kim wrote to me today and asked
"In Illustrator, we make our PDF files via File > Save As: Adobe PDF. But Illustrator makes the PDF file sizes VERY large, even when saving as Smallest File Size. What can we do about this?"
All recent versions of Illustrator default to saving a copy of the entire .AI file inside the saved PDF file, so that Illustrator can open and edit the PDF file later. This makes it handy if you don't want to keep track of a separate .AI file and .PDF file. You can have a single PDF file that is editable in Illustrator, but also viewable by others with Adobe Reader. The big downside is that the file is large.
The workaround is to just save and maintain a .AI version of the file for editing purposes, and a separate .PDF file for sending you your print vendor or for others to view. Here's how:
First, make sure you've saved your work as an Illustrator .AI file.
Next, choose File > Save a Copy, choose Adobe PDF for the Format, and click the Save button, you'll see the dialog pictured below.
Just deselect the Preserve Illustrator Editing Capabilities option, then click the Save PDF button. You may see the warning pictured below. If so, just click the OK button, as long as you've previously saved a .AI version of the file.
The exported PDF file should be much smaller.