It is possible to compress a PDF in Preview. I have done it many times and the results vary in terms of savings and quality.

*In the Preview app on your Mac, open the PDF, then choose File > Export.

*Click the Quartz Filter pop-up menu, then choose Reduce File Size.


On a Mac since 1984.
Currently: 24" M1 iMac, M2 Pro Mac mini with 27" BenQ monitor, M2 Macbook Air, MacOS 14.x; iPhones, iPods (yes, still) and iPads.