How to compress a PDF on a Mac

Email and upload forms often reject big PDFs. You can make them smaller on your own Mac, without sending them to a website.

Free: Preview's Reduce File Size

In Preview, choose File ▸ Export, then pick Reduce File Size from the Quartz Filter menu. It is quick, but it can make images noticeably blurry.

With Stillpage

1. Choose Compress in the sidebar and drop in one or more PDFs.
2. Pick Standard (keeps quality) or Smallest (for on-screen reading).
3. Click Compress. Each result shows the size before and after.

Files that are already compact are reported as such rather than made worse.

Why some PDFs are so big

Almost always it's images: scans, photos and screenshots stored at a high resolution. Text-only PDFs are usually small. Embedded fonts add a little too.

Keeping files small from the start

• Scan documents at 300 dpi in greyscale unless colour matters.
• When you combine scans into one file, compress the result once at the end rather than each piece.
• For email, aim for under about 10 MB; many mail services reject attachments around 20–25 MB.

Common questions

Will compressing make it look worse? Standard keeps text sharp and images readable for printing. Smallest goes further and is meant for reading on screen; zoom in on a photo-heavy page before sending it.

Is my original changed? No. Stillpage writes a new file (name.compressed.pdf) next to the original, or into a folder you choose.