FinderBuddyA folder of scanned invoices, a semester of lecture slides, or forty signed contracts: exporting each PDF from Preview with a smaller size gets old fast.
This guide shows how to compress many PDFs at once on a Mac, keep the originals safe, and check that the results are still readable. If you only have one file, start with how to reduce PDF file size on Mac.
Method 1: Build a free Compress PDFs Quick Action
Automator, which comes with every Mac, can apply Preview's compression filter to any number of PDFs. You set it up once and then it lives in Finder's right-click menu.
- Open Automator from Applications, choose New Document, then Quick Action.
- At the top, set Workflow receives current to PDF files in Finder.
- Search the action library for Apply Quartz Filter to PDF Documents and drag it into the workflow.
- Automator offers to add a Copy Finder Items action so your originals aren't changed. Click Add, and choose a folder for the copies, for example a "Compressed" folder on your desktop.
- In the Quartz filter action, choose Reduce File Size.
- Choose File → Save and name it "Compress PDFs".
Now select any number of PDFs in Finder, right-click, and choose Quick Actions → Compress PDFs. The smaller copies land in the folder you picked.
The built-in filter can make scanned text soft. If it does, create the gentler custom filter described in our single-PDF guide; custom filters show up in the same list.
Method 2: Sharper results with Ghostscript in Terminal
Ghostscript is a free PDF engine that gives you more control over quality. It isn't built in, so install it once with Homebrew: brew install ghostscript. Then run:
cd ~/Desktop/pdfs
mkdir -p compressed
setopt nullglob nocaseglob
for f in *.pdf; do
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook \
-dNOPAUSE -dBATCH -dQUIET \
-sOutputFile="compressed/$f" "$f"
done/ebookresamples images to about 150 DPI, which keeps scanned text readable.- Use
/screen(about 72 DPI) for the smallest files, or/printer(about 300 DPI) when the PDFs will be printed. - Compressed copies go into the
compressedfolder with the same names.
Method 3: Compress a batch from the right-click menu
FinderBuddy puts Compress PDF straight into Finder's right-click menu, with no workflow to build and no Terminal. Select one PDF or a folder's worth, right-click, and choose FinderBuddy → Compress PDF. The same menu also merges, splits, and extracts pages.
Everything is processed on your Mac, which matters for contracts, invoices, and IDs. See pricing or read the setup guide.
Check the results before you send them
- Compare sizes. In Finder's list view, sort by Size. Scanned PDFs usually shrink a lot; PDFs that are mostly typed text are already small and can even get bigger. Keep the original when that happens.
- Zoom in on small print. Open a few of the compressed files and zoom to 200% on fine text, signatures, and tables.
- Don't count on a ZIP file. PDFs are already compressed inside, so zipping a folder of them rarely saves much space.
Need one file instead of many? See how to merge PDF files on Mac, then compress the result.
Frequently asked questions
- Can Preview compress multiple PDFs at once?
- Not directly. Preview exports one PDF at a time. An Automator Quick Action with the Apply Quartz Filter to PDF Documents action uses the same Reduce File Size filter on as many PDFs as you select.
- How do I compress PDFs on Mac without losing quality?
- Use a gentler setting: a custom Quartz filter at around 150 DPI, or Ghostscript's /ebook preset. Both keep text readable while still shrinking scanned pages.
- Why did my PDF get bigger after compressing?
- PDFs that are mostly text or vector graphics are already efficient. Re-saving them adds overhead without removing anything. Keep the original in that case.
- Is it safe to compress PDFs online?
- Online tools upload your documents to someone else's server. For contracts, bank statements, or IDs, compressing on your Mac keeps them private.