How to Compress a PDF on iPhone (Free, No App)

A PDF that is too large to attach, upload, or share stops you cold on an iPhone — an email bounces, a portal rejects the file, or it fills your iCloud storage. Fortunately you do not need to download a compressor app to fix it.

Here is how to compress a PDF on your iPhone for free, without installing anything.

Your compression options on iPhone

• The Files app has a Quick Action called Optimize File Size that compresses a PDF with one tap
• A browser-based compressor in Safari gives you control over how much to shrink the file
• Many App Store compressors hide the useful features behind subscriptions or add watermarks

Compress a PDF on iPhone in Safari

Open a browser-based compressor and shrink the file in seconds — your document is processed on your phone, so it never has to be uploaded anywhere:

1. 1Open the Compress PDF tool in Safari on your iPhone.
2. 2Tap to choose a file, then select your PDF from the Files app or iCloud Drive.
3. 3Pick a compression level — light keeps text and images crisp, while heavier compression makes the smallest file.
4. 4Tap compress and review the new file size.
5. 5Download the smaller PDF back to your device and share it from the Files app.

This works even for a document that arrived as an email attachment: save it to Files first, then open it in the compressor.

Using the built-in Files Quick Action

For a very quick fix with no quality options, open the Files app, long-press the PDF, tap Quick Actions, then Optimize File Size. It replaces the file with a smaller version and needs no app at all. Because it overwrites the original, duplicate the PDF first if you want to keep the uncompressed copy.

Start small at the source

If even strong compression will not get the file small enough, re-scan or re-save it with less detail — lower resolution and grayscale for a scan cuts size dramatically. Compressing then becomes a final polish instead of a battle, and the result stays readable.