The short answer: open a PDF compressor in Safari, add the file from your Files app, pick a compression preset, and download the smaller version. No app to install, no account, and the file never leaves your iPhone.
The usual scenario: you're away from your desk, someone needs a document emailed now, and the PDF is 40 MB of scanned pages that won't attach to anything. Your iPhone can fix this in about two minutes.
Step by step in Safari
- Save the PDF to Files if it isn't there already. From Mail: open the attachment, tap share, "Save to Files." From WhatsApp or Drive: share/download it into Files.
- Open PDFEdit's compress tool in Safari (Chrome on iOS works too).
- Tap to add the PDF. The iOS file picker opens — browse to the file in Downloads, iCloud Drive, or On My iPhone.
- Choose a preset:
- Recommended — the default. Re-renders pages at 150 DPI, cuts roughly 35–65%, keeps text crisp. Right for most jobs.
- Extreme — 96 DPI, cuts roughly 60–85%. For strict email limits or huge scans. Some visible softening.
- Less — 220 DPI, cuts roughly 15–35%. When the file is only slightly too big and quality matters.
- Compress and download. The tool shows before/after sizes. Safari saves the result to Files — tap the download icon in the toolbar to open it.
- Share it. From Files, tap share and send via Mail, WhatsApp, or AirDrop.
iPhone-specific tips
Wi-Fi helps for big files. Nothing uploads — but Safari does the heavy processing locally, and iPhones throttle background work more aggressively on cellular. For files over ~30 MB, Wi-Fi makes it smoother.
Close heavy apps first. Compression runs in browser memory. If Safari reloads the page mid-compression on an older iPhone, it's a memory squeeze — close a few apps and retry.
Photos aren't PDFs. If the "document" is photos in your camera roll, convert them first with an image-to-PDF tool, then compress the resulting PDF. (Phone photos are huge — this two-step routinely turns 30 MB of photos into a 3 MB PDF.)
Check the result before sending. Open the compressed file in Files, zoom in on a page of text. If it's crisp, send it. If you used Extreme and the small print suffered, that's the trade-off — keep the original.
What shrinks most on iPhone
- Scanned documents — the biggest wins. Phone and flatbed scans are usually far higher resolution than needed.
- Photo collections saved as PDF — very compressible.
- Text-only PDFs — barely shrink; there's no image data to cut. If one of these is "too big," it's usually embedded fonts, and compression won't help much.
The email target
If you're compressing to email the file: Gmail and Outlook cap attachments at ~25 MB, and encoding overhead eats about a third of that in transit. Aim for ~18 MB or less in the final file. If Extreme still doesn't get you there, split the PDF into parts instead.
Reduce size before the PDF even exists
Often the smartest compression happens before you make the PDF:
Camera settings. If you're photographing documents, your iPhone shoots at 12–48 MP by default — absurd overkill for text. You can't easily lower the camera resolution per-shot, but scanning apps (Apple Notes scan, Adobe Scan, Google Drive) capture at sensible resolutions and produce dramatically smaller PDFs than the Camera app + image-to-PDF route.
Scan, don't photograph. The Notes app's document scanner (new note → camera → "Scan Documents") auto-detects page edges, corrects perspective, and outputs a compact PDF. A 10-page Notes scan is typically 1–3 MB; the same 10 pages as camera photos converted to PDF can be 30 MB.
Choose grayscale for text. Scanning apps usually offer color/grayscale/black-and-white. For text documents, grayscale cuts size roughly 3× versus color with zero readability loss.
Sharing the smaller file from iPhone
Once compressed, getting it to the recipient:
- Mail: attach from Files (new email → attach → browse Files). Watch the ~18 MB practical ceiling for Gmail/Outlook.
- WhatsApp/Telegram: share directly from Files — their limits (2 GB on WhatsApp) swallow anything email can't.
- AirDrop: for nearby Apple devices, the fastest option and no size anxiety at all.
- Files app link: iCloud Drive files can be shared as links (long-press → Share → "Copy iCloud Link") for anything too big to attach.
Pro move: keep both versions in Files — Contract.pdf (original) and Contract-small.pdf (compressed). When someone asks for "the high-res version," you have it.
When the iPhone struggles
Two honest limitations:
- Very large files (100 MB+) may exceed what mobile Safari comfortably processes. For those, use a desktop browser — the tool is identical, the RAM isn't.
- Password-protected PDFs need unlocking first (unlock tool) — the compressor can't open a file it can't read.
- Extremely image-heavy PDFs (photo albums, design portfolios) compress more slowly because there's simply more image data to process. Give it time; the progress indicator shows it's working.
Neither is an iPhone-specific flaw; they're physics and encryption. Everything else works exactly as on desktop.
Do it with PDFEdit
Reduce PDF size on your iPhone — free, three clearly-labeled presets with live size readout, processed 100% in Safari on your device.
The bottom line
Your iPhone is a perfectly good PDF compressor — the browser does the work, the Files app holds the result, and the whole job takes less time than finding and installing a "free" compressor app (which would want a subscription anyway). Compress, check, send.
