Why iPhone makes this awkward
The Files app on iOS can open and share PDFs, but it has no built-in "reduce file size" option. That leaves people installing apps that upload the document to a server just to shrink it — not ideal for anything private. The simpler route is a browser tool: the Unfuss PDF compressor runs entirely in Safari, so the file is compressed on your iPhone and never uploaded.
Step by step on iPhone
- Open Safari and go to unfuss.app/compress-pdf.
- Tap the drop zone and choose your PDF from Files, iCloud Drive, or a recent attachment. (If it's in Mail or another app, tap Share → Save to Files first.)
- Pick a level — Balanced for a good size, Strong for the smallest.
- Tap download when it finishes, then Save to Files or share it straight away.
It works best on scanned and image-heavy PDFs — exactly the ones that end up too big to email or upload from a phone.
A note on quality
The compressor re-renders pages as optimised images, so a scan comes out much smaller. Text-based PDFs are already small, so there's less to gain there. If a document is still too big, send fewer pages with Split PDF — that also works in Safari.
Frequently asked
Can I compress a PDF on iPhone without an app?
Yes. Open unfuss.app/compress-pdf in Safari and compress the PDF right in the browser — no App Store download, no account, and the file never leaves your phone.
Is my PDF uploaded from my iPhone?
No. The compressor runs in Safari on your device, so the PDF is processed on the iPhone itself and never sent to a server.
Where do I find the PDF to select?
Tap the drop zone and use the file picker to browse Files, iCloud Drive, or recent attachments. Save PDFs to Files first if they're in an email or another app.
Which level should I choose on mobile?
Start with Balanced. If the PDF is still too big to attach or upload, switch to Strong. It works best on scanned and image-heavy PDFs.