The fastest way to shrink a PDF on Mac
The built-in Preview app on your Mac can reduce a PDF's file size in under a minute without needing to read anything. Open the PDF in Preview, go to File > Export, then change the Quartz Filter dropdown from "None" to "Reduce File Size". Save the file with a new name, and you're done. The file will be noticeably smaller, though the image quality will drop slightly — this trade-off is usually worth it for PDFs you're emailing or storing.
If that reduction isn't enough, or if Preview's quality loss bothers you, the next step is to use Mac's built-in compression tools or a dedicated app. The method you choose depends on how much smaller the file needs to be and whether you care more about keeping the original quality or getting the smallest possible file.
Key Takeaways
- Preview's Reduce File Size filter shrinks most PDFs by 30 to 50 percent in one step, with no software to install.
- Compressing images within the PDF before saving works better than compressing the PDF itself if the file contains many photos.
- Removing pages, deleting embedded fonts, or stripping metadata can reduce file size when the PDF contains data you don't need.
- Third-party apps like PDFtk or Automator workflows offer more control but take longer to set up than Preview.
Using Preview's built-in compression
Preview is the simplest route because it's already on your Mac. Open the PDF you want to shrink, then click File in the menu bar and select Export. A dialog box will appear with several options. Look for the dropdown that says "Quartz Filter" — it will probably say "None". Click that dropdown and select "Reduce File Size".
Before you click Save, give the file a new name so you don't overwrite the original. Something like "filename-compressed" works well. Then choose where you want to save it and click Save. Preview will process the file, which usually takes a few seconds. The new file will be smaller, though images inside it will be compressed and may look slightly softer or less sharp.
If the result is still too large, or if the quality loss is too much, you can try exporting again with different settings. Some PDFs compress better than others depending on what's inside them — a PDF full of photographs will shrink more than one full of text and straightforward graphics.
Compressing images before you save the PDF
If the PDF contains many high-resolution photos or scans, the real problem is usually the images themselves, not the PDF format. Compressing those images before you create or save the PDF will shrink the file more effectively than compressing the finished PDF.
If you created the PDF yourself from images or documents, go back to the original files and compress the images first. You can do this in Preview by opening each image, going to Tools > Adjust Size, and lowering the width or height. A photo that's 3000 pixels wide can usually be shrunk to 1200 or 1500 pixels without looking noticeably worse on screen. Then save the smaller image and create the PDF again.
If someone else created the PDF and you can't access the original images, you can still extract the images from the PDF, compress them, and rebuild the PDF. This is more work, but it often produces better results than compressing the finished PDF. Apps like PDFtk or online tools can help, though they require more steps than Preview's one-click method.
Removing pages and unnecessary content
Sometimes a PDF is large because it contains pages or data you don't actually need. If you're only keeping certain pages, removing the rest will shrink the file when ready. In Preview, you can delete pages by opening the PDF, clicking View in the menu bar, and selecting Thumbnails. A sidebar will appear showing every page as a small image. Right-click any page you want to remove and select Delete. Then save the file.
PDFs can also contain hidden data — embedded fonts, metadata, or form fields — that add to the file size even though you can't see them. Preview doesn't have a straightforward way to strip this data, but exporting with the Reduce File Size filter usually removes some of it automatically. If you need more control, third-party apps like PDFtk or online PDF tools can let you remove specific elements, though this requires more technical steps.
Using third-party apps for more control
If Preview's compression isn't enough and you regularly work with PDFs, a dedicated app gives you more options. PDFtk (free, command-line tool) and Automator (free, built into Mac) both let you compress, remove pages, and strip metadata in ways Preview doesn't. These tools take longer to learn but give you precise control over what gets removed and how much compression happens.
Paid apps like PDF Squeezer or Compressor also exist, but they're rarely worth the cost unless you're processing hundreds of PDFs. For most people, Preview handles the job well enough. Test Preview first — if it solves your problem, you're done. If not, then explore other options.
What to expect from each method
| Method | Time to complete | File size reduction | Quality loss |
|---|---|---|---|
| Preview Reduce File Size filter | 1 minute | 30–50% | Slight (images soften) |
| Compress images before saving | 5–15 minutes | 40–70% | Minimal if done carefully |
| Remove unnecessary pages | 2–5 minutes | Varies (10–90% depending on pages removed) | None (you choose what's removed) |
| Third-party app (PDFtk, Automator) | 10–30 minutes (setup) then 1 minute per file | 30–60% | Varies by settings |
The table above shows what you can realistically expect from each approach. Start with Preview's Reduce File Size filter — it's the fastest and works for most PDFs. If that doesn't shrink the file enough, move to compressing images or removing pages. Save the third-party tools for situations where you're processing many PDFs and want to automate the process.
Most people find that Preview alone solves the problem. The compression happens in the background without you having to understand technical settings, and the file size drop is usually noticeable enough to make a difference when emailing or uploading.
Frequently Asked Questions
Will compressing a PDF make it look bad?
Preview's compression softens images slightly but usually keeps text sharp. For PDFs you're emailing or viewing on screen, the difference is barely noticeable. If the PDF is for printing or contains detailed graphics, test the compressed version first before deleting the original.
Can I undo compression if I don't like the result?
Yes — because you saved the compressed version with a new name, your original file is still there. You can always go back to it. If you already overwrote the original, you can't recover the quality, so always save compressed PDFs with a different filename.
Why is my PDF so large when it only contains text?
Text-only PDFs are usually small. If yours is large, it likely contains embedded fonts, scans of pages instead of actual text, or hidden metadata. Try Preview's Reduce File Size filter first. If that doesn't help much, the PDF probably contains images or scans that are taking up space.
Does compressing a PDF change the content or make it unreadable?
No. Compression only reduces image quality and removes some metadata — the actual content stays the same and remains fully readable. You can open and use a compressed PDF exactly as you would the original.
What's the smallest a PDF can get?
That depends on what's inside it. A text-only PDF can be very small — under 100 KB. A PDF full of high-resolution photos might be several MB even after compression. There's no universal minimum; you're limited by the content itself.