Guide

How to compress a PDF on iPhone

A PDF full of scanned pages or photos can get big fast, and unlike a Mac, an iPhone has no built-in tool to shrink one. Apple's Mail app quietly raises your attachment ceiling instead — which still leaves you with a large file to share. Here's how to actually compress a PDF on iPhone or iPad.

Key takeaways

Built-in tool: Files and Markup cover viewing and marking up; compression comes from a dedicated app.
App: PDFPivot (our app), or any iPhone PDF app with an on-device Compress tool.
Internet: Compression runs on the device, offline.
Cost: Free; PDFPivot shows ads, with an optional subscription to remove them.

What's the fastest way to shrink a PDF's file size on iPhone?

Open the PDF in an app with a Compress tool, pick a compression level, and save or share the result. On-device compression shrinks embedded images and strips redundant data without uploading anything.

Does Mail already handle large PDFs on iPhone?

Partly. When an attachment is too big for a regular email, Mail on iPhone can use Mail Drop to upload it to iCloud automatically and send the recipient a download link instead — with Mail Drop, you can send attachments up to 5GB, from Mail on iPhone, iPad, or Mac (Apple Support). That answers "can I send it" and leaves "is this a reasonably sized file" open.

Mail Drop applies once you're sending through Apple's own Mail app. Upload portals, job applications, work email systems, and apps like WhatsApp usually enforce their own, far smaller limits, and a recipient still has to download a large file over their own connection. Compression still matters everywhere beyond Apple Mail.

How do you compress a PDF on iPhone, step by step?

Install a PDF app that compresses on-device. PDFPivot (our app) does this locally on your iPhone or iPad.
Open the PDF and select Compress or Reduce Size.
Choose a compression level — light for barely-noticeable shrinkage, strong for the smallest file when image quality can give a little.
Save the compressed PDF to Files, or share it directly through the Share sheet, Mail, or AirDrop.

What can go wrong when compressing a PDF on iPhone?

The file is still too big after compressing. Compression mainly reduces embedded image resolution, so a PDF already built from low-resolution scans is close to its floor. Try a stronger compression level.
The compressed PDF looks blurry. Step back to a lighter setting if fine print or photo detail matters.
Compressing barely changed the file size. Text-only PDFs are already small; the biggest gains come from scanned or photo-heavy documents.

Compression works well right after you scan a paper document or edit its text and images, and just before you add a signature and send it on. For tools that keep working across platforms without uploading your file, see our offline PDF editors comparison.

Frequently asked questions

Does iPhone have a built-in PDF compressor?

PDF compression on iOS comes from a dedicated app. Files and Markup handle viewing and marking up, and an app such as PDFPivot on iPhone and iPad shrinks the file itself.

Can I compress a PDF on iPhone without an internet connection?

Yes, if the app compresses on-device. PDFPivot shrinks the file locally on your iPhone; web-based compressors need an upload and a connection.

How big a PDF can I email from an iPhone?

With Mail Drop, Apple's Mail app can send attachments up to 5GB by uploading them to iCloud automatically, from an iPhone, iPad, or Mac. Many recipients' own inboxes still reject much smaller files in practice, so compressing a heavy, scan-based PDF down to a few megabytes is still worth doing.