If you are on Windows, you can do this work-around as I posted long time ago:
"I’ve just discovered that instead of using “save as PDF” or printing to PDF, you use Microsoft print to PDF you can get small file sizes specially when you are printing a table with lots of thumbnail pictures. The difference is huge. A table with 32 pictures, at first had 35MB, which is impractical to send as email attachment. It all came down to 330KB when using the Microsoft virtual printer. For me, it’s a very useful tip and I wanted to share with the community."
You can also vote here as a sugestion, so Coda can fix it. It’s a big issue for me too.