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 about two minutes without installing anything. Open the PDF in Preview, go to File > Export, choose PDF from the format dropdown, then click the Quartz Filter dropdown and select "Reduce File Size". Save the file with a new name. This method works for most PDFs and cuts the file size by 20 to 50 percent depending on what's in the document.

If Preview's built-in filter doesn't shrink the file enough, or if you need more control over the compression, the other methods below give you different trade-offs between file size and image quality. Most people find one of these three approaches solves the problem without needing paid software.

Key Takeaways

  • Preview's Reduce File Size filter is the fastest method and requires no additional software or setup.
  • Compressing images within the PDF using ColorSync Utility gives you more control but takes longer than Preview's automatic filter.
  • Removing pages, deleting embedded fonts, or stripping metadata can shrink PDFs that contain unnecessary content.
  • The file size reduction depends on what's in the PDF — documents with photos compress much more than text-only files.

Using Preview's built-in compression filter

Open the PDF you want to shrink in Preview. If Preview isn't your default PDF app, right-click the file, select "Open With", and choose Preview. Once the PDF is open, click File in the menu bar at the top of the screen.

From the File menu, select Export. A save dialog will appear. At the bottom of this dialog, you'll see a dropdown that says "Format" — click it and make sure "PDF" is selected. Below that, find the "Quartz Filter" dropdown, which usually shows "None" by default. Click this dropdown and select "Reduce File Size".

Type a new filename in the "Save As" field so you don't overwrite the original. Click Save. Preview will process the file and save the compressed version. Check your Downloads folder or wherever you chose to save it. The new file should be noticeably smaller than the original.

This method works best for PDFs that contain photographs or scanned images. Text-only PDFs may not shrink much because there's less to compress. If the result still isn't small enough, try one of the methods below.

Compressing images inside the PDF with ColorSync Utility

If you need more aggressive compression, you can target the images within the PDF directly. Open Finder and navigate to Applications > Utilities > ColorSync Utility. This is a built-in Mac tool that most people never open, but it has a PDF compression feature.

In ColorSync Utility, click File > Open and select your PDF. Then go to Filters in the menu bar. You'll see several filter options — select "Reduce File Size". A panel will appear on the right side showing compression settings. You can adjust the image quality slider: moving it left makes the file smaller but reduces image quality, while moving it right keeps better quality but results in a larger file.

After adjusting the slider to your preference, click Apply. The tool will process the PDF and show you the new file size. Go to File > Save to save the compressed version. ColorSync Utility gives you more control than Preview's automatic filter, but the trade-off is that you have to manually adjust settings and the process takes longer.

Removing unnecessary pages or content

Sometimes a PDF is large because it contains pages you don't need. Open the PDF in Preview and look at the page thumbnails on the left side. If you see pages you want to remove, right-click on the thumbnail and select Delete. Preview will remove that page from the document.

You can also delete pages in bulk. Hold down the Command key and click multiple page thumbnails to select them, then right-click and delete. When you're done removing pages, go to File > Export and save the PDF with a new name. This method is especially useful if you've received a large PDF but only need certain pages from it.

Some PDFs also contain embedded fonts or metadata that add to the file size without being visible. Preview doesn't have a built-in way to strip these, but the ColorSync Utility method above will remove some of this hidden data as a side effect of recompressing the file.

When to use Mac's built-in tools versus other options

Preview and ColorSync Utility handle most compression needs without cost or installation. Use Preview's Reduce File Size filter first — it's the fastest and works for the majority of PDFs. If that doesn't shrink the file enough and you need to preserve image quality, switch to ColorSync Utility and adjust the compression slider yourself.

If you regularly compress PDFs and want a more streamlined interface, third-party apps like PDF Squeezer or PDFtk exist, but they cost money and aren't necessary for occasional use. The built-in tools are powerful enough for most situations.

Keep in mind that aggressive compression reduces image quality. If you're sending a PDF to someone who needs to read small text or view detailed images, use a less aggressive compression setting. If the PDF is just for archiving or sharing via email, you can compress more aggressively.

Checking your file size before and after

To see how much space you've saved, open Finder and locate both the original PDF and the compressed version. Right-click each file and select "Get Info". A window will pop up showing the file size in bytes. Compare the two numbers to see your reduction percentage.

For example, if the original is 50 MB and the compressed version is 15 MB, you've reduced the file size by about 70 percent. Most people find that Preview's automatic filter achieves 20 to 50 percent reduction, depending on the PDF's content. PDFs with many photographs compress more than those with mostly text.

Frequently Asked Questions

Will compressing a PDF make it blurry or hard to read?

Preview's automatic filter usually maintains readability for text and most images. If you use ColorSync Utility and move the quality slider too far left, text can become pixelated. Start with a moderate setting and check the result before saving. You can always recompress if the quality isn't acceptable.

Can I compress a PDF that's password-protected?

Preview can open password-protected PDFs if you enter the password, but you may not be able to export or compress them if the PDF has restrictions set by the creator. Try opening it in Preview first — if it opens, you can usually compress it. If compression fails, the PDF likely has export restrictions.

What's the smallest file size I can get?

The smallest possible size depends on what's in the PDF. Text-only documents don't compress much because text is already efficient. PDFs with photographs can shrink 50 to 80 percent. There's no universal minimum — it varies by content. Experiment with Preview first, then try ColorSync if you need smaller.

Do I need to keep the original PDF after compressing it?

Keep the original if the PDF contains important images or if you might need the higher quality later. If you're compressing just to save space or send via email, you can delete the original once you confirm the compressed version looks acceptable.

Can I compress multiple PDFs at once?

Preview and ColorSync Utility compress one file at a time. If you have many PDFs to compress, you can repeat the process for each one, but there's no batch compression feature in the built-in Mac tools. Third-party apps offer batch processing, but the free tools require individual processing.