How to Compress a PDF on iPhone: 5 Free Methods That Work

PDF files on your iPhone can balloon in size — scanned documents, photos saved as PDFs, and files with embedded images can easily hit 20 MB or more. When you need to email a PDF, upload it to a form with a size limit, or just free up storage, compressing that file becomes essential. Here are the best free ways to shrink PDFs right on your iPhone.

Why Compress PDFs on iPhone?

• Email attachments — most email providers limit attachments to 25 MB
• Upload limits — many job applications, government forms, and school portals cap file sizes at 2-5 MB
• Storage space — compressed PDFs take up less room on your device and in iCloud
• Faster sharing — smaller files send quicker over AirDrop, iMessage, and messaging apps
• Better performance — large PDFs can cause apps to lag when scrolling or annotating

Method 1: Using Adobe Acrobat Reader (Free)

Adobe Acrobat Reader for iPhone includes a free compression feature:

1. Install Adobe Acrobat Reader from the App Store.
2. Open the app and import your PDF.
3. Tap the three-dot menu next to the file.
4. Select Compress PDF from the options.
5. Choose your compression level (Low, Medium, High).
6. The compressed file is saved alongside the original.

Adobe's compression typically reduces file size by 40-70% depending on the content. Scanned documents and image-heavy PDFs see the biggest reductions. The free tier includes basic compression — advanced options require a subscription.

Method 2: Using PDF Expert by Readdle

PDF Expert is one of the best PDF apps on iOS:

1. Install PDF Expert from the App Store.
2. Open your PDF in the app.
3. Tap the ... menu and select Reduce File Size.
4. Choose a quality preset or customize the DPI and image quality.
5. Save the compressed version.

PDF Expert gives you granular control over compression. You can target specific file sizes, adjust image resolution, and remove redundant data. The free version includes basic compression.

Method 3: Using Apple Shortcuts

You can create a shortcut that reduces image quality inside PDFs:

1. Open the Shortcuts app.
2. Tap + to create a new shortcut.
3. Add Find Files — set it to find the selected PDF.
4. Add Make PDF from Images with reduced quality settings.
5. Add Save File to output the compressed version.
6. Name it "Compress PDF" and add it to your home screen.

This works best for PDFs that are essentially images (like scanned documents). It will not compress text-based PDFs as effectively.

Method 4: Online Compressors via Safari

Browser-based tools work on iPhone without installing anything:

1. Open Safari on your iPhone.
2. Visit a compression site like iLovePDF, Smallpdf, or PDF24.
3. Tap Select PDF file and choose your document.
4. Choose the compression level.
5. Download the compressed file to your Files app.

These tools typically achieve 50-80% size reduction. The trade-off is that your file is uploaded to a server. Avoid this for sensitive documents like tax returns, medical records, or legal contracts.

Method 5: Using the Files App (iOS 16+)

The Files app can create compressed ZIP archives of your PDFs:

1. Open the Files app and locate your PDF.
2. Long-press the PDF file.
3. Tap Compress from the context menu.
4. A ZIP archive is created for easy sharing.

Note: This creates a ZIP file which reduces size for transfer, but the PDF inside stays the same when extracted. For actual PDF compression, use the methods above.

Compression Results: What to Expect

• Scanned documents (images): 60-80% reduction possible
• Image-heavy PDFs: 40-70% reduction
• Text-only PDFs: 10-30% reduction (they are already small)
• Mixed content: 30-60% reduction

Tips for Better Compression

• Remove unnecessary pages before compressing — fewer pages means smaller output
• Lower scan resolution — 150 DPI is sufficient for most documents
• Use black and white for text documents — color scans are 3-5x larger
• Flatten form fields before compressing — see our guide on how to flatten PDFs
• Compress images first — reduce photos before creating the PDF

Frequently Asked Questions

Will compressing a PDF reduce its quality?

It depends on the compression level. Light compression preserves visual quality while reducing file size significantly. Heavy compression may make images blurry but keeps text readable. Always check the result before sharing.

Can I compress a password-protected PDF?

Most tools require you to unlock the PDF first. Remove the password, compress, then re-protect if needed. See our guide on removing PDF passwords.

Is there a size limit for compressing PDFs on iPhone?

Desktop-class apps like PDF Expert handle files up to several hundred MB. Online tools typically cap uploads at 100-200 MB on their free tiers. For very large files, split them first using our PDF splitter for iPhone.