Flatten PDF to print

I make layered documents (usually with text boxes and clip art) and then convert them to PDF to save and print. However, the layers create huge files and take up too much space and take too long to download and print.

How can I flatten these PDFs so they are smaller and easy to store/print. Is there a way to add the option to "print to PDF" to my word program? Or is there another program that I can download that will do this?

I have a macbook pro, running High Sierra and Office 2016.