How to Compress a PDF on iPhone, Mac and Windows (Free)
The quickest free way on any device is a browser tool that compresses on your device: open Compress PDF, add the file and choose a target such as 1 MB. Macs also have a built-in option in Preview, and iPhones a basic Shortcuts action, but both give you little control.
On a Mac (Preview)
- Open the PDF in Preview.
- Choose File → Export.
- Set Quartz Filter to Reduce File Size and save under a new name.
Apple notes the result “may be of lower quality”. In practice this filter often makes scanned pages very blurry, and it can make some text-only PDFs larger. Compare before you send.
On an iPhone or iPad
- Open Compress PDF in Safari.
- Tap the drop area and choose the PDF from Files.
- Pick a target (for example 1 MB or 500 KB) and tap Compress. The result goes to Downloads in Files.
The Shortcuts app has an “Optimize File Size of PDF” action, but testers report it shrinks scans only slightly.
On Windows or Android
Windows has no built-in PDF compressor (“Microsoft Print to PDF” does not reduce images). Use the browser tool in Edge or Chrome; on Android, open it in Chrome and pick the file from Files or Drive.
Why some PDFs barely shrink
Compression works on the images inside a PDF. Text-only PDFs are already small, and some scans are stored efficiently already. See Why your PDF won’t compress for the details.