You need to send a PDF from your iPhone but it's too large to attach to an email or upload to a portal. There's no built-in compression tool in iOS, but several reliable options exist โ from browser-based tools that work in Safari to dedicated apps. Here's what works and what the tradeoffs are.
Option 1: Use a Browser-Based Tool in Safari
The fastest method that requires no app installation: open Safari on your iPhone, go to WukongPDF at www.wukongpdf.com, and use the PDF Compression tool directly in the browser. Tap Upload, select the PDF from your Files app, choose a compression level, and download the compressed result.
After compression, the file downloads to your Downloads folder in the Files app. From there you can share it directly via Mail, Messages, AirDrop, or any other app. The whole process โ open site, upload, compress, download โ takes about a minute on a reasonable connection.
Option 2: Use the iOS Shortcuts App
The Shortcuts app on iPhone can compress PDFs locally โ without uploading to any server. This is the best option for sensitive documents you don't want to send to external servers.
- Open the Shortcuts app and tap the + button to create a new shortcut
- Add the action "Get File" to select a PDF from Files
- Add the action "Compress PDF" โ this uses iOS's built-in PDF rendering to reduce file size
- Add "Save File" or "Share" to output the compressed result
The Shortcuts compression is less aggressive than dedicated compression tools โ it typically reduces file size by 20-40% rather than 50-70%. For documents that are moderately oversized, it's sufficient. For heavily image-laden files that need significant reduction, a dedicated tool produces better results.
Option 3: Dedicated PDF Apps
Several PDF apps on the App Store include compression features. Adobe Acrobat's free iOS app offers compression for PDFs in your account. PDF Expert (paid) includes local compression without server uploads. Foxit PDF Reader also has compression capability on iOS.
The advantage of dedicated apps over browser tools is that they work offline and process files locally. The disadvantage is the initial download and often a subscription or purchase cost for compression features. If you regularly need to compress PDFs on iPhone, a dedicated app is worth it. For occasional compression, the browser tool is more practical.
Prevent Large Files: Compress at Scan Time
If the large PDF is a document you scanned with your iPhone, you can prevent the size problem before it occurs. iPhone's built-in document scanner (in Files, Notes, or the Camera app) saves scans at a reasonable quality. Third-party scanning apps often save at higher quality by default โ check the settings for a "Compression" or "File Size" option.
Microsoft Lens and Adobe Scan both offer quality settings that significantly affect output file size. Setting quality to "Normal" or "Optimized" rather than "High" or "Best" produces scans that are 60-80% smaller with no meaningful difference in readability for most documents. For a receipt or a form you're submitting digitally, lower quality is entirely adequate.
How to Share the Compressed PDF From iPhone
Once the compressed PDF is in your Files app, tap and hold the file to bring up the share sheet. From there you can attach it to an email (Mail), send via iMessage or WhatsApp, upload to Google Drive or Dropbox, or use AirDrop to send to a nearby Mac or iPhone. If the file is still larger than an email attachment limit after compression, use the "Save to Files" option and share a cloud storage link instead โ upload to iCloud Drive and share the link via the Files app share sheet. This bypasses attachment size limits entirely and delivers the full-quality PDF Compression result without the size constraint.