Compress a PDF on iPhone, free and in Safari

The steps in Safari

1. Open the compressor in Safari: this page, or getpdfs.app/compress-pdf. The first time you pick a file, the page fetches its engine (4.6 MB, once); after that it is kept on the phone.
2. Tap Choose files. iOS opens the Files browser. Go to Recents, iCloud Drive, On My iPhone or Downloads and tap your PDF. Several files at once are fine; each is compressed on its own.
3. Pick a preset, or type a size target. Email is selected by default (pictures at 110 dpi): right for attachments and uploads read on a screen. If a form asks for a number such as 1 MB or 200 KB, type it in the Size target field and pick KB or MB. The size pages do this for you: 1 MB, 500 KB, 200 KB, 100 KB.
4. Tap Compress and read the result. It shows the size before and after, and on a target, the resolution it took to get there.
5. Tap Download PDF. Safari saves the file and a download button appears next to the address field. The copy is named after your file with -compressed on the end, so your original stays as it was.
6. Find it in Files, under Browse, then Downloads. Apple’s support article “Where to find downloads on your iPhone or iPad” places that folder in iCloud Drive by default (checked on 11 October 2026).

What the iPhone has built in

iOS opens, views and marks up PDFs in Quick Look and the Files app. For making them smaller, several guides (iDownloadBlog among them, checked on 11 October 2026) describe an Optimize File Size quick action: in Files, touch and hold the PDF, then tap Quick Actions, then Optimize File Size. We could not find it in Apple’s own documentation, and sources disagree on whether it writes a copy or replaces the original, so check before you rely on it.

What it does not have is a choice. There is no preset, no size target and no report of what changed. If you just want “smaller” and do not mind by how much, try it first. If a portal names a number, or you want to see what the compression cost, use the steps above.

Why iPhone scans and photos are big

A PDF made from iPhone camera photos is mostly photographs at full camera resolution. A 12-megapixel photo is 4032 by 3024 pixels and about 3 MB as a JPEG, so 5 photos make a PDF of about 15 MB. Scans made with the Notes app or the Files scanner are pictures of pages too, and on paper with colour, stamps or shadows they add up fast.

These are real outputs from our test file of 5 photos at 12 megapixels (14.7 MB), measured on 11 October 2026:

The text in a PDF is never touched by compression, so typed text stays sharp. In a scan, the “text” is part of the photo and softens with it; check the smallest print at 200 percent before you send. If the PDF is still to be made, smaller photos in give a smaller PDF out: the pictures to PDF guide covers that side.

Sharing it onward from the phone

The compressed copy is an ordinary file in Files, so every app can reach it:

• Mail: in a new message, tap the attachment button and pick the file from Downloads, or open the file in Files and tap Share, then Mail. Providers cap attachments at around 20 to 25 MB; the too big to email guide has the table.
• WhatsApp and other chats: attach it as a document, not as a photo, so it is sent as the file it is.
• Portal uploads in Safari: the portal’s upload button opens the same Files browser; pick the copy from Downloads. Portals that ask for 100 KB or 200 KB are covered in the 100 KB guide.

The honest part: memory, and what this cannot do

Very large files can be too much for Safari. Safari gives each tab a limited amount of memory, and an iPhone does not tell a web page how much. A typical phone PDF of tens of MB is fine; a 500-page scan of several hundred MB may make Safari reload the page instead of finishing, on an older iPhone especially. When that happens, split the file into parts and compress each, or do that one job on a computer.

Compression cannot shrink text. A PDF that is mostly typed text is already small, and the tool says so and gives you the original back rather than a “compressed” file of the same size.

It is lossy for pictures. Photos and scans are re-encoded, and detail that is dropped does not come back. Keep the original in Files; send the small copy.

Check that nothing is uploaded, on the phone itself

The proof fits in your hand. Compress one file with the network on, so the engine is fetched and kept. Then turn on aeroplane mode, reload the page and compress another file. It still works, because the PDF is processed in Safari on your iPhone and there is nowhere for it to go. The same test works on Android; the Android guide has the steps for Chrome.