Word 2011 creates a 66 MB PDF from a 1 MB Word file
Courtesy of the ever-useful Dr. Drang, you can try using a Quartz Filter to downsample the images to reduce the file size, often without any apparent reduction in quality.


Open ColorSync Utility and click on the Filters tab.
Add a new filter, give it a name you like.
Click on the grey arrow, select Color Image Sampling under Add Image Effects Component.
Enter 150 in the resolution box.


Now we need to create an Automator service to apply the filter to the PDF file.


Open Automator and make a new Service.
Change the top drop-down to PDF Files.
Add the Apply Quartz Filter to PDF Documents action, and select the filter you just created in the drop-down.
Save it with a name of your choice.


Now you should be able to right click on a PDF file, and you should see the service you created near the bottom of the menu. Click it, and a few seconds later you should have a smaller PDF.