How to compress a PDF on iPhone

On iOS 26 and later, open the PDF in the Preview app, tap the Actions menu button next to the file name, tap Export and turn on the options that make the images smaller. It works best on scanned pages and photos – text takes up almost no room. Below: the steps, a way that shows the new size before you save, and what to do if the file is still too big.

With Preview (iOS 26 and later)

1. Open the PDF in the Preview app.
2. Tap the Actions menu button next to the file name, then tap Export.
3. Choose PDF and turn on Optimize Images for Screen and Save Images as JPEG.
4. Tap Done, choose where to save the copy and tap Save.

The original stays as it was. Apple's guide

Why do some PDFs barely shrink?

It's the images that take up the space in a PDF. A scanned letter or a PDF made from photos is a stack of pictures, and those can get a lot smaller. A PDF exported from Word or a bank statement is mostly text and fonts, which already take very little room, so there's little to gain. Tools that still make such a file much smaller do it by turning the pages into pictures. Then the text gets blurry, and you can no longer search or copy it.

Compress with Udfyld

Udfyld is an iPhone app for PDFs, and it works on iOS 17 and later. It compresses on your iPhone, so nothing is uploaded.

1. Open the PDF in Udfyld, from Files, or from Mail with Share › Udfyld.
2. Tap Compress and choose Small (smallest, for email), Medium (a good balance, sharp text) or Original.
3. Udfyld shows the size before and after for each choice, and a preview of a page.
4. Tap Use, then save or share. Udfyld saves a copy, so the original isn't changed.

Pages with text are never turned into pictures. Only scanned pages and photos are made smaller, and a page without colour is saved in greyscale.

Still too big to email?

Mail on iPhone offers Mail Drop when an attachment is too big: the file goes to iCloud, and the recipient gets a link that works for 30 days, for files up to 5 GB. Online tools such as iLovePDF and Smallpdf can compress too, but they upload your PDF to their servers. Think twice before doing that with a payslip, a contract or anything with your ID number on it.

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