- Compress a PDF in Acrobat on your computer
- Compress lots of PDFs at once
- Compress a PDF online with Acrobat on the web
- Compress a PDF on a Mac with Preview
- Which method suits you?
- Why compressing sometimes does little
- Always save a copy first
- Check the size before and after
- What the Preview options really do
- What if it's still too big?
- My verdict
- Frequently asked questions
To compress a PDF in Acrobat, choose Save as Other then Reduced Size PDF, pick the Acrobat version your readers can open and save. On the web, use Convert then Compress a PDF. On a Mac, open Preview, choose File then Export and set the Quartz Filter to Reduce File Size.
A PDF that bounces back from an email or won't upload to a form is a small crisis at the worst moment. The good news is that shrinking one takes about a minute, and you probably already have the tool. Below are the three routes: Acrobat on your computer, Acrobat on the web and Preview on a Mac, plus the setting that can quietly stop a compressed file opening for the person you send it to.
Compress a PDF in Acrobat on your computer
- Open the PDF in Acrobat.
- On Windows choose Menu, then Save as Other, then Reduced Size PDF. On a Mac the path starts at File instead of Menu.
- In the dialog box, pick an Acrobat version from the Make compatible with menu.
- Select OK, then choose a location, type a filename and select Save.
The compatibility menu is the bit people skip. Adobe says to choose a version that everyone who uses the PDF can open. Choose an old version and the file opens almost anywhere but may compress less. Choose a new one and you get a smaller file that older software might struggle with. If you're sending to a client you've never met, play safe and pick the older option.
Compress lots of PDFs at once
If you've got a folder of scans to shrink, you don't need to repeat that process for each one. In the same Reduced Size PDF dialog, select Apply to Multiple Files. Add the PDFs in the Arrange documents window, press OK, then choose the output folder, the filename style and whether you're happy to overwrite the originals. Choose a new folder and the originals stay safe.
Compress a PDF online with Acrobat on the web
- On the Acrobat on the web homepage, select Convert, then Compress a PDF.
- Choose where the file is, pick it and select Continue.
- Add more files if you want to compress several together.
- Pick a compression level and select Compress.
Adobe says this method works by removing embedded fonts, compressing images and eliminating unnecessary items. The new file is named with _compressed added to the end and saved to Adobe cloud storage, and you get a notification with a link to download it. Your original is left as it was.
Compress a PDF on a Mac with Preview
- Open the PDF in Preview.
- Choose File, then Export.
- In the Quartz Filter pop-up menu, choose Reduce File Size.
- Click Save. If Preview asks about replacing the existing file, click Cancel and type a new name in the Export As box so you keep the original.
Apple is upfront about the trade-off: when a PDF is compressed it may be of lower quality than the original. That matters most for scanned pages and photographs. Text-only PDFs usually look fine. Export dialog checkboxes give you some control: Optimize images for screen, Save images as JPEG and Create Linearized PDF, which Apple says optimizes the file for fast loading in web browsers.
Which method suits you?
| Method | Best for | Watch out for |
|---|---|---|
| Acrobat, Reduced Size PDF | One file or a batch on your computer | The Make compatible with setting |
| Acrobat on the web | Quick one-offs without installing anything | The result is stored in Adobe cloud storage |
| Preview on a Mac | A fast shrink with nothing to install | Lower image quality than the original |
Why compressing sometimes does little
If your PDF is mostly text and still huge, there may be big embedded images or lots of embedded fonts. If it's a stack of photos or scans, compression is going to bite harder. None of these tools can give you a tiny file and perfect image quality at the same time, so try the result at full zoom before you send it.
Always save a copy first
Compressing is a one-way trip for image quality. Save the compressed version under a new name, and keep the original somewhere you can find it. If your PDF started life as a blog post or a report, my guide to turning a blog post into a PDF shows how to make a lighter file from the start.
Check the size before and after
It sounds obvious, but note the file size before you start. Right-click the file and look at its properties on Windows, or select it and use Get Info on a Mac. Then check again after compressing. If the number barely moved, the file is probably mostly text and fonts, and a different approach, such as removing pages you don't need, will help more than a stronger setting.
What the Preview options really do
- Optimize images for screen trades print quality for a smaller file. Fine for email, not for sending to a printer.
- Save images as JPEG converts the images, which makes them lighter but can soften fine detail.
- Create Linearized PDF arranges the file so it starts showing quickly in a web browser. It's about speed of loading, not necessarily size.
If the PDF is going to be printed professionally, check with the printer before you compress it. A file that looks fine on a screen can look rough on paper, and you can't get the lost detail back from a compressed copy.
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What if it's still too big?
Compression has limits. If the file is still too large for the form or email you're using, try these in order: remove pages you don't need, re-export from the original document at a lower image quality, or share a link to the file instead of attaching it (my guide to sharing big design files has the same tricks). A link also avoids the common problem where one inbox rejects what another accepts.
My verdict
Use Acrobat's Reduced Size PDF if you've got it, and choose a compatibility version your readers can open. Use Acrobat on the web for a one-off, or Preview on a Mac when you just want it smaller now. Always check the result at full zoom before it goes anywhere.
Frequently asked questions
How do I compress a PDF?
In Acrobat choose Save as Other, then Reduced Size PDF, pick a compatibility version and save. On the web use Convert, then Compress a PDF. On a Mac use File, Export, and set the Quartz Filter to Reduce File Size in Preview.
Will compressing a PDF reduce quality?
It can. Apple warns that a compressed PDF may be of lower quality than the original, so keep your original and check the compressed version.
Can I compress several PDFs at once?
Yes. In Acrobat's Reduced Size PDF dialog, select Apply to Multiple Files and add the PDFs.
Where does Acrobat on the web save the compressed file?
It saves the file as filename_compressed in Adobe cloud storage and offers a download link.
What does Make compatible with mean?
It sets which Acrobat versions can open the reduced file. Adobe advises choosing a version that everyone who uses the PDF can open.
