How to merge PDFs on your Mac
Merge PDFs on a Mac without a website: Finder's Create PDF, Preview's sidebar, or drag them with Shift held onto Koi's Merge and pick the order first.
The short answer
Two ways, and neither uploads it
Your Mac can shrink a PDF by itself: Preview has a Reduce File Size filter. Koi does it in one drag, with three strengths and the size shown before you save. Both keep the file on your Mac, which matters for a contract, a bank statement or a scan of your passport.
We make Koi, so read this with that in mind. Everything about Koi here is what version 1.12 does. Preview's steps come from Apple's own guide, checked October 20, 2026.
Preview
Compress a PDF with Preview
- Open the PDF in Preview.
- Choose File, then Export.
- In the Quartz Filter menu, choose Reduce File Size.
- Give the copy a name and click Save.
Apple notes that the smaller file can look worse than the original, and that the size and quality you get depend on the options you pick. Apple's guide has the details.
Koi
Compress a PDF with the Shift wheel
- Start dragging the PDF in Finder or on your desktop.
- While you're still holding it, press and hold Shift. A wheel opens round your pointer.
- Drop the PDF on Compress.
- Pick Light, Balanced or Strong. The size before and after shows, with the pages as they'll look.
- Save. “Report compressed.pdf” lands beside the original and shows in Finder.
- Light, Balanced and Strong keep the pictures inside at 220, 150 or 96 pixels to an inch, saved again as JPEGs.
- Its words, links and pages stay as they were. Text stays text you can search and copy.
- The original is never touched. When its folder can't be written to, the copy goes to Downloads.
- A PDF a password keeps shut doesn't open.
What to expect
Which PDFs get much smaller?
Both ways work on the pictures inside the PDF. A scan, or a PDF full of photos, has a lot to give. A PDF that's mostly text has little in it to shrink, so don't expect it to drop much. Try Balanced first, and Strong only if the file still won't fit.
More
The rest of the PDF wheel
The same wheel also organizes a PDF's pages, edits its metadata, splits it, merges several, and converts it to Word, Pages, PowerPoint, Excel, JPG, PNG, text or Markdown. All of it on your Mac. More on the Shift wheel.
Price
What it costs
Preview is free and already on your Mac. Koi has no free plan: Pro is $20 a month, or $192 a year, after a 3-day free trial that needs a card. Lifetime is paid once, from $59. The Shift wheel uses no AI, so it never counts against Koi's usage. See the plans.
Keep exploring
Drag a file. Hold Shift.
Drag any file on your Mac and hold Shift: crop a photo, edit a video, merge or compress a PDF, convert Word, slides or sheets, or unzip. All on your Mac.
How to convert Word to PDF on your Mac
Convert a Word file to PDF on a Mac without Word: export it from Pages, use Save as PDF, or drag it with Shift held onto Koi's PDF. Done on your Mac.
A photo and video toolbox, one Shift key away
Koi's Shift wheel: drag any image or video on your Mac, hold Shift, and compress, crop, redact or convert it, or trim and edit a video. Nothing is uploaded.
Support
Frequently asked questions
Open it in Preview, choose File, Export, and set the Quartz Filter to Reduce File Size, then save. Apple notes the smaller file can look worse than the original.
No. Koi compresses it on your Mac with Apple's PDFKit and Quartz and saves the copy beside the original. Nothing is sent.
Yes. Koi's Compress saves the pictures inside smaller and leaves the words, links and pages as they were.
Compressing works on the pictures inside a PDF. One that's mostly text has little to shrink.