How to compress a PDF on a Mac

Make a PDF small enough to email — choose 75%, 50%, 25% or 10% of its size, on your Mac.

Built in: open the PDF in Preview → File → Export → Quartz Filter: Reduce File Size. It often over-compresses images.

With Garlic

Start dragging the PDF and hold ⌘ Command for the tools.
Drop on Compress and pick a size — say 50%.
Garlic tries the gentle way first (text stays sharp) and only flattens pages if it has to.

Hold ⌥ Option instead for the Email preset: about half the size, no questions.

Everything happens on your Mac; nothing is uploaded. macOS 13 or later.