The fastest way to reduce a PDF on Mac
The built-in Preview app on your Mac can shrink a PDF without installing anything. Open the PDF in Preview, go to File > Export, then choose Quartz Filter from the dropdown menu and select Reduce File Size. Save the file with a new name. This works for most PDFs and typically cuts the file size by 20 to 50 percent, depending on what the PDF contains.
If Preview's built-in filter does not shrink the file enough, or if you need more control over the compression, you have other options on Mac that range from free web tools to paid desktop software. The method you choose depends on how much smaller the file needs to be and whether you want to keep the PDF's image quality high.
Key Takeaways
- Preview's Reduce File Size filter is free and built into macOS, requiring no download or setup.
- Dragging a PDF into the Mac Mail compose window automatically compresses it when you send it.
- Online tools like Smallpdf and ILovePDF work in your browser and do not require you to install software, though they upload your file to their servers.
- For large batches of PDFs or very high compression needs, dedicated Mac apps like PDF Squeezer or PDFtk offer more options but cost money.
Using Preview to compress in one step
Preview is the simplest route because it is already on your Mac. Open the PDF you want to shrink, then click File in the menu bar. Select Export (not Save, which overwrites the original). A dialog box opens.
In the dialog, look for a dropdown menu that says Format or shows a file type. Click it and select PDF. Below that, you will see another dropdown labeled Quartz Filter. Click it and choose Reduce File Size. Then click Save. Preview compresses the PDF and saves it as a new file, leaving your original untouched.
This method works best for PDFs that contain mostly text or simple graphics. If your PDF is full of high-resolution photographs, the compression may make images blurry. You can test this by opening both the original and compressed versions side by side to see if the quality loss is acceptable.
Compressing a PDF through Mail
If you are sending the PDF to someone by email, Mac can compress it automatically. Open Mail and start a new message. Drag the PDF file directly into the compose window. A dialog appears asking if you want to send the file at its current size or a smaller size. Click Reduce Size.
Mail compresses the PDF before attaching it, so the recipient gets a smaller file. This is useful for one-off situations, but it does not save a compressed copy on your Mac — only the email attachment is smaller. If you need to keep a compressed version of the file for later use, use Preview instead.
Online tools that work in your browser
Web-based PDF compressors like Smallpdf, ILovePDF, and Compress PDF do not require you to install anything. You upload your PDF to their website, they compress it on their servers, and you download the result. Most offer a free tier that lets you compress one or two PDFs per day without paying.
The trade-off is that your PDF file is uploaded to someone else's server. If the PDF contains sensitive information, this may not be acceptable. Read the privacy policy of whichever tool you choose. Most say they delete uploaded files after a few hours, but you are trusting their word.
These tools often give you a slider or menu to choose compression strength, so you can balance file size against image quality. They also tend to compress more aggressively than Preview, which can be useful if you need the file much smaller.
Paid Mac apps for batch compression
If you regularly compress PDFs or need to shrink many files at once, dedicated apps like PDF Squeezer or PDFtk Pro run on your Mac and do not upload files anywhere. These cost between $10 and $30 and let you set compression levels, choose what to remove (like embedded fonts or metadata), and process multiple files in a batch.
Batch processing is the main advantage here. If you have 50 PDFs to shrink, you can select all of them, set your compression preferences once, and let the app process them all without clicking through each one. For occasional use, this is overkill, but for regular work it saves time.
What affects how much a PDF can shrink
A PDF's file size depends mostly on what it contains. A PDF made from scanned photographs will be much larger than one made from text and simple shapes, and it will also compress less without losing visible quality. A PDF with embedded fonts or high-resolution images will shrink more than one that is already optimized.
Compression works by removing or reducing the quality of images, stripping out metadata, and eliminating unused fonts. If your PDF is mostly text, compression will have little effect because there is not much to remove. If it is mostly images, compression can cut the file size significantly, but the images will look worse.
Before you compress, check the file size of the original. Right-click the PDF and select Get Info. The size in bytes appears in the window. After compression, check again to see how much space you actually saved. This tells you whether the compression method is worth using for your situation.
Comparing your options
| Method | Cost | Setup | Compression strength | Best for |
|---|---|---|---|---|
| Preview | Free | None — already on Mac | Moderate | Quick one-off compression |
| Mail attachment | Free | None | Moderate | Sending files by email |
| Online tools (Smallpdf, ILovePDF) | Free tier available | None — browser only | Strong | One or two files, no privacy concerns |
| PDF Squeezer or PDFtk Pro | $10–$30 | Download and install | Strong, customizable | Batch processing or frequent use |
Frequently Asked Questions
Will compressing a PDF make it blurry?
It depends on what the PDF contains. Text stays sharp because compression does not affect text quality. Images will become blurry if you use strong compression, especially photographs. Preview's Reduce File Size filter is gentle and usually preserves readability. If you need stronger compression, test it on a copy first to see if the quality loss bothers you.
Can I compress a PDF that is password protected?
Preview and most online tools will not compress a password-protected PDF unless you unlock it first. Open the PDF in Preview, go to File > Properties, and look for a security section. If the PDF is locked, you will need the password to unlock it before compression works.
What is the smallest file size I can get?
That depends on the original content. A text-heavy PDF may only shrink 10 to 20 percent because there is little to compress. A photo-heavy PDF can shrink 50 to 80 percent, but images will look noticeably worse. There is no universal smallest size — it is a trade-off between file size and quality.
Do online PDF tools keep my files?
Most reputable tools like Smallpdf and ILovePDF delete files from their servers within a few hours of upload. However, they do briefly store your file on their servers, so do not use them for confidential documents. If privacy is critical, use Preview or a paid Mac app instead.
Can I undo compression if I do not like the result?
No — compression removes data from the PDF, and you cannot get it back. Always save the compressed version with a new filename so your original stays intact. That way, if the compressed version does not work for you, you still have the original to try a different method.