Got a 47 MB PDF that needs to be under 10 MB for an email attachment? I’ve been there more times than I can count. macOS actually has built-in tools for PDF compression, but they’re buried in menus most people never find. And honestly, the default “Reduce File Size” filter in Preview is… aggressive. It murders image quality.
I spent two weeks testing every method I could find – native macOS tools, online services, and third-party apps. Here’s what actually works in 2026, ranked by how well each method balances file size reduction with quality preservation.
If you need a full-featured PDF editor alongside compression, check out our guide to the best free PDF editors – several of them handle compression well on Mac.
Quick Comparison: Mac PDF Compression Methods
| Method | Avg. Compression | Quality Loss | Batch Support | Offline | Best For |
|---|---|---|---|---|---|
| Preview (Quartz Filter) | 60-80% | High | No | Yes | Quick one-off compression |
| Custom ColorSync Filter | 40-70% | Low-Medium | No | Yes | Balanced quality + size |
| Smallpdf | 50-75% | Low | Yes (paid) | No | Best quality preservation |
| ILovePDF | 55-80% | Low-Medium | Yes | No | Multiple compression levels |
| Adobe Acrobat Online | 40-65% | Low | No | No | Professional documents |
| PDF Squeezer | 50-75% | Configurable | Yes | Yes | Power users, bulk work |
| Ghostscript (Terminal) | 40-85% | Configurable | Yes (scripting) | Yes | Developers, automation |
Method 1: Preview’s Built-in Quartz Filter (Fastest, But Read This First)
Every Mac has this. Open your PDF in Preview, go to File > Export, and in the “Quartz Filter” dropdown pick “Reduce File Size.” Done. A 45 MB file becomes 4 MB in seconds.
Sounds perfect, right? Not exactly. The default Quartz filter downsamples images to 512×512 pixels maximum. For a presentation with charts or a scanned document, the result looks like it was faxed in 1998. Text-heavy PDFs with minimal images? Works fine. Anything with photos or detailed graphics? Keep reading.
Steps:
- Open the PDF in Preview (right-click > Open With > Preview)
- Click File > Export (not “Save” – that won’t show filter options)
- Click the “Quartz Filter” dropdown
- Select “Reduce File Size”
- Choose where to save and click Save
I tested this on five different PDFs. Results:
| File Type | Original Size | After Preview Filter | Reduction | Quality |
|---|---|---|---|---|
| Text-only report | 2.1 MB | 1.8 MB | 14% | Perfect |
| Presentation (20 slides) | 38 MB | 3.2 MB | 92% | Terrible |
| Scanned contract | 12 MB | 1.4 MB | 88% | Barely readable |
| Mixed text + charts | 8.5 MB | 2.1 MB | 75% | Charts are blurry |
| Photo portfolio | 67 MB | 5.8 MB | 91% | Useless |
Bottom line: Preview’s default filter is a sledgehammer. Good for text documents, bad for everything else.
Method 2: Custom ColorSync Filter (The Hidden Power Move)
Here’s what most Mac users don’t know – you can create a custom compression filter that preserves way more quality than the default. It takes about 2 minutes to set up, and you only need to do it once.
How to create a custom filter:
- Open ColorSync Utility (search for it in Spotlight or find it in Applications > Utilities)
- Click the “Filters” tab at the top
- Find “Reduce File Size” in the list, click the arrow to expand it
- Click the dropdown next to it and select “Duplicate Filter”
- Name it something like “Medium Compression” or “Balanced PDF”
- Expand your new filter and click on “Image Sampling”
- Change the scale to something higher – I use 75% instead of the default
- Set resolution to 150 DPI (the default goes much lower)
- Under “Image Compression,” set JPEG quality to 0.65-0.75
- Close ColorSync Utility – it saves automatically
Now when you go to Preview > File > Export > Quartz Filter, your custom filter appears in the dropdown. I got my 38 MB presentation down to 9 MB with readable charts using this method. Not as dramatic as the 3.2 MB the default filter produced, but actually usable.
The sweet spot I found after testing: 150 DPI resolution, 70% JPEG quality, 75% image scale. Cuts most files by 40-60% without visible quality loss on screen. Print quality does suffer a bit, so if someone needs to print the PDF at full resolution, this isn’t ideal.
Method 3: Smallpdf (Best Online Option for Mac)
Smallpdf consistently gave me the best balance between compression and quality across all the online tools I tested. Their compression algorithm is smarter than most – it analyzes what’s in the PDF and adjusts accordingly rather than applying a blanket reduction.
How to use it:
- Go to smallpdf.com/compress-pdf
- Drag your PDF onto the page (or click to browse)
- Wait for upload and processing
- Choose “Basic Compression” (free) or “Strong Compression” (Pro)
- Download the compressed file
Free limits: 2 tasks per day. Max file size 5 GB. Basic compression only (typically 20-40% reduction). Pro is $9/month for unlimited tasks and stronger compression.
My 38 MB presentation came out at 14 MB with basic compression – charts were crisp, photos looked good. Strong compression (Pro) got it to 8 MB with minimal visible difference.
Privacy note: Smallpdf deletes uploaded files after 1 hour. If you’re compressing sensitive documents (contracts, medical records, financials), the custom ColorSync filter or an offline tool is a better pick.
Method 4: ILovePDF (Best Free Online with Compression Levels)
ILovePDF gives you three compression levels for free, which is more control than most online tools offer. The interface is straightforward – no account required for basic use.
Steps:
- Go to ilovepdf.com/compress_pdf
- Upload your PDF
- Pick a compression level: Extreme, Recommended, or Less Compression
- Click “Compress PDF”
- Download the result
Free limits: 1 file at a time, up to 100 MB per file. You get a handful of free tasks per day (they don’t publish the exact number, but I hit a limit after about 10 files). Premium is $4/month.
“Recommended” mode hit a nice middle ground in my testing – 55% average reduction with decent quality. “Extreme” was too aggressive for anything with images. “Less Compression” barely did anything (15-20% reduction on most files).
They also have a desktop app for Mac (free with limits, $4/month for unlimited). The desktop version processes files locally, which is better for privacy.
Method 5: Adobe Acrobat Online (Conservative but Reliable)
Adobe’s online compressor is more conservative than the others – you’ll get smaller reductions (typically 30-50%), but the output quality is consistently high. Makes sense, since Adobe literally invented the PDF format.
How to use it:
- Go to adobe.com/acrobat/online/compress-pdf.html
- Upload your file (drag and drop or browse)
- Choose compression level: High, Medium, or Low
- Download the result
Free limits: 1 file per session without signing in. Sign in with a free Adobe account for a few more. No batch processing on the free tier. Acrobat Pro ($19.99/month) for unlimited use.
Look, $20/month just for PDF compression is absurd. But if you already pay for Creative Cloud, the compression in the full Acrobat app (Acrobat > File > Reduce File Size) is the best I’ve tested. It just costs too much to recommend buying specifically for this.
Method 6: PDF Squeezer (Best Paid Mac App)
PDF Squeezer is a native Mac app that costs $12.99 one-time on the App Store. If you compress PDFs regularly (weekly or more), it pays for itself in time saved versus using online tools.
What makes it worth the price:
- Drag-and-drop batch compression (drop a folder of PDFs)
- Four preset compression levels plus fully custom settings
- Preview before saving – see the compressed version alongside the original
- Automator and Shortcuts support for workflows
- Everything stays on your Mac – no uploads
In my testing, PDF Squeezer’s “Default” preset averaged 55% reduction with quality comparable to Smallpdf’s Pro mode. The “Extreme” preset pushed to 75%+ but with noticeable quality loss on images. You can dial in exactly the DPI, JPEG quality, and color model you want.
The batch processing is the real selling point. I dropped a folder of 23 PDFs (total 380 MB) and had them all compressed to 145 MB in under 40 seconds. Doing that one-by-one with an online tool would take forever.
Method 7: Ghostscript in Terminal (For Developers and Automation)
If you’re comfortable with Terminal, Ghostscript gives you the most control over PDF compression on Mac. Install it via Homebrew and you get a command that handles everything from basic compression to full resampling.
Setup:
brew install ghostscriptBasic compression command:
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
-dPDFSETTINGS=/ebook \
-dNOPAUSE -dBATCH -dQUIET \
-sOutputFile=compressed.pdf input.pdfThe -dPDFSETTINGS flag controls compression level:
| Setting | DPI | Use Case | Typical Reduction |
|---|---|---|---|
| /screen | 72 | Screen viewing only | 70-85% |
| /ebook | 150 | Email attachments, web | 50-70% |
| /printer | 300 | Standard print quality | 20-40% |
| /prepress | 300+ | High-quality print | 10-25% |
For batch processing, wrap it in a simple shell script:
for f in *.pdf; do
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
-dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -dQUIET \
-sOutputFile="compressed_${f}" "$f"
doneI use the /ebook setting for 90% of my compression tasks. It brings a 50 MB scan-heavy PDF down to around 12-15 MB while keeping text sharp and images readable on screen.
Which Method Should You Use?
Quick one-off, text-heavy PDF: Preview’s built-in filter (Method 1). Takes 10 seconds.
Need decent quality with images: Custom ColorSync filter (Method 2) if you want to stay offline, or Smallpdf (Method 3) if you don’t mind uploading. For more on online compression tools, see our detailed guide on how to compress PDF files online free.
Regular compression needs: PDF Squeezer ($12.99) if you do this weekly. The batch processing alone justifies the cost.
Automation or scripting: Ghostscript. No question. Free, scriptable, and the most granular control available.
Sensitive documents: Stick to offline methods (Preview, ColorSync, PDF Squeezer, or Ghostscript). Don’t upload confidential files to online services.
Tips for Getting Smaller PDFs on Mac
Sometimes the best compression happens before you create the PDF in the first place.
- Resize images before inserting them. A 4000×3000 photo in a presentation is overkill when it displays at 800×600. Resize in Preview first (Tools > Adjust Size).
- Use “Export as PDF” instead of “Print to PDF” in some apps. Pages and Keynote create smaller PDFs through File > Export > PDF than through the print dialog. The difference can be 30-40%.
- Check for embedded fonts. Some PDFs embed full font families when they only use a few characters. Ghostscript’s
/ebooksetting subsets fonts automatically. - Remove unnecessary pages first. Use Preview to delete pages you don’t need before compressing. Drag pages out in the sidebar thumbnail view.
- Scan at the right DPI. Scanning at 600 DPI when 200 DPI is enough creates files 9x larger than needed. Most text documents look fine at 200 DPI, photos at 300 DPI.
Also worth checking out: our roundup of the best free PDF readers for Mac, since some of them include compression features built in.
Frequently Asked Questions
Can I compress a PDF on Mac without losing quality?
No compression method preserves 100% of the original quality – that’s the tradeoff. But you can minimize visible quality loss. The custom ColorSync filter method (150 DPI, 70% JPEG quality) produces files that look identical on screen for most documents. For truly lossless reduction, you’re limited to font subsetting and metadata stripping, which typically only saves 5-15%.
Why does Preview’s “Reduce File Size” make my PDF look so bad?
Preview’s default Quartz filter downsamples all images to a maximum of 512×512 pixels and applies heavy JPEG compression. Apple designed it for the smallest possible file size, not for quality preservation. Use a custom ColorSync filter (Method 2) to get better results with Preview’s export feature.
What’s the best free way to compress a large PDF on Mac?
For a single file under 100 MB, ILovePDF’s “Recommended” compression level gives the best free results without installing anything. For files you’d rather keep offline, creating a custom ColorSync filter takes 2 minutes of setup and works indefinitely. For multiple files, install Ghostscript through Homebrew – it handles batch compression with a single terminal command.
Does macOS Sequoia have better PDF compression than older versions?
The core Quartz filter hasn’t changed significantly since macOS Monterey. What did improve in Sonoma and Sequoia is Preview’s overall PDF handling speed and stability with large files. The compression algorithms and quality output remain essentially the same across recent macOS versions.
How small can I make a PDF on Mac without it being unreadable?
It depends entirely on the content. A text-only 10 MB PDF can safely shrink to 1-2 MB. A 50 MB PDF full of high-resolution photos can typically go to 10-15 MB before quality visibly degrades on a Retina display. My rule of thumb: use the /ebook setting in Ghostscript (150 DPI) as the floor for anything that needs to remain readable.