Working with PDFs on Mobile: Complete Guide for Phones and Tablets

You're at a coffee shop. Someone emails you a contract to sign. Your laptop is at home.

What do you do?

Ten years ago, this was a problem. Today, you can handle pretty much any PDF task from your phone. Sign that contract, compress that bloated file, merge those documents—all from your pocket.

Here's everything you need to know about working with PDFs on mobile.

What Your Phone Can Already Do (No Apps Needed)

Before we talk about apps, let's cover what's built in:

iPhone (iOS)

Files app:

• Open and view any PDF
• Basic markup (highlight, draw, add text)
• Sign documents (built-in signature)
• Share via AirDrop, email, messages
• Save to iCloud Drive

Quick Look:

• Preview PDFs from email or messages
• Tap to view, pinch to zoom
• Markup without opening another app

Built-in signing:

• Open PDF in Files or Books
• Tap markup icon
• Tap +, then Signature
• Draw your signature, place it, done

Android

Google Drive:

• View PDFs directly
• Basic annotation
• Share easily

PDF Viewer (varies by phone):

• Samsung, Pixel, OnePlus have built-in viewers
• Basic viewing and sharing
• Some support markup

Chrome browser:

• Opens PDFs inline
• Download or share
• No editing, just viewing

What Built-In Tools Can't Do

Both iOS and Android struggle with:

• Merging multiple PDFs
• Splitting documents
• Significant compression
• Converting to/from Word
• Complex editing
• OCR for scanned documents

For these, you need apps or web tools.

Web-Based Tools: The Universal Solution

Here's the thing: You don't always need an app.

PDF Smaller works on any mobile browser:

• iPhone Safari
• Chrome on Android
• Any modern mobile browser

What you can do from your phone:

• Compress PDFs - Shrink files for email
• Merge multiple PDFs - Combine files
• Split PDFs - Extract pages
• Add signatures - Sign documents
• Rotate pages - Fix orientation
• Convert formats - PDF to Word and back

How it works:

1. Open your browser
2. Go to the tool you need
3. Upload your file (works from Files, Drive, etc.)
4. Process
5. Download result

The advantage: No app to install. Works on any device. Always up to date.

The disadvantage: Needs internet connection. File upload might be slower on mobile data.

Best PDF Apps for iPhone

PDF Expert (by Readdle)

Best for: Power users who work with PDFs daily

What it does:

• View, annotate, edit PDFs
• Fill forms
• Sign documents
• Sync across Mac, iPhone, iPad

Pricing: Free basic features, $79.99/year for full access

Standout feature: Fluid page navigation and excellent Apple Pencil support on iPad

Adobe Acrobat Reader

Best for: People in Adobe's ecosystem

What it does:

• View and annotate
• Fill and sign
• Comment and collaborate
• Access Adobe cloud storage

Pricing: Free to view and sign; $9.99/month for editing features

Standout feature: Integration with Adobe Document Cloud and desktop Acrobat

Microsoft 365 (Office)

Best for: Office users who occasionally need PDF features

What it does:

• View PDFs
• Sign documents
• Convert PDFs to Word (with subscription)
• Scan documents to PDF

Pricing: Included with Microsoft 365 subscription ($6.99+/month)

Standout feature: Seamless Word/Excel/PDF workflow

Apple Books

Best for: Reading PDFs, not editing them

What it does:

• Store and organize PDFs
• Beautiful reading experience
• Sync across Apple devices
• Basic markup

Pricing: Free (built into iOS)

Standout feature: Excellent PDF library management

Best PDF Apps for Android

Xodo PDF Reader & Editor

Best for: All-around PDF needs on Android

What it does:

• View, annotate, sign
• Fill forms
• Collaborate in real-time
• Cloud storage integration

Pricing: Free with optional premium features

Standout feature: Real-time collaboration for team annotation

Adobe Acrobat Reader

Best for: Cross-platform Adobe users

Same as iOS version—reliable, feature-rich, Adobe-integrated.

Foxit PDF Editor

Best for: Serious editing on mobile

What it does:

• Full PDF editing
• AI-assisted features
• Form filling
• Security features

Pricing: Free basic, subscription for advanced features

Standout feature: Smart Redact automatically finds sensitive info

Google Drive

Best for: Basic viewing without installing anything

What it does:

• Open PDFs directly
• Basic annotation
• Seamless cloud storage
• Easy sharing

Pricing: Free

Standout feature: No installation needed; works immediately

PDFelement

Best for: Feature-rich editing without Adobe pricing

What it does:

• Edit, annotate, convert
• OCR for scanned docs
• AI writing assistance
• Cross-platform sync

Pricing: Free trial; $79.99/year for full features

Standout feature: AI-powered features for summarizing and translating

Common Mobile PDF Tasks

Signing a Document

The scenario: Contract in your email. Need to sign and return it.

On iPhone (built-in):

1. Open PDF in Files or Mail
2. Tap the markup icon (pen)
3. Tap + → Signature
4. Draw signature (saves for reuse)
5. Place, resize, done
6. Share back

On Android (with app):

1. Open PDF in Xodo or Adobe Reader
2. Find signature or fill & sign tool
3. Draw or upload signature
4. Place on document
5. Save and share

Using web tool:

1. Go to PDF Smaller Sign tool
2. Upload PDF
3. Draw, type, or upload signature
4. Place signature
5. Download signed PDF

Time: 2-3 minutes, any method

Compressing a Large PDF

The scenario: 25MB PDF. Email limit is 10MB. Need to shrink it.

Best approach: Use web tool (most effective on mobile)

1. Open browser
2. Go to PDF Smaller Compress
3. Upload PDF
4. Wait for compression
5. Download smaller version

Results: Usually 50-80% size reduction

Time: 1-2 minutes depending on file size and connection

Merging Multiple PDFs

The scenario: Three separate PDFs need to become one document.

Using web tool:

1. Go to PDF Smaller Merge
2. Upload all three files
3. Arrange order
4. Merge
5. Download combined PDF

Using app (PDF Expert):

1. Open first PDF
2. Use merge/append feature
3. Add additional PDFs
4. Save merged file

Time: 2-3 minutes

Converting PDF to Word

The scenario: Need to edit the text in a PDF. Word is easier.

Using web tool:

1. Go to PDF Smaller PDF to Word
2. Upload PDF
3. Wait for conversion
4. Download Word document
5. Edit in Word app

Results: Works well for text-based PDFs. Complex layouts may need cleanup.

Adding Text to a PDF

The scenario: Need to fill in information that's not a form field.

On iPhone:

1. Open PDF in Files
2. Tap markup
3. Tap + → Text
4. Type your text
5. Position and resize
6. Save

Using PDF Smaller Edit:

1. Upload PDF
2. Add text boxes where needed
3. Type content
4. Download edited PDF

Extracting Pages

The scenario: 50-page document, but you only need pages 5-10.

Using web tool:

1. Go to PDF Smaller Split
2. Upload PDF
3. Select pages 5-10
4. Extract
5. Download smaller PDF

Using app:

1. Open PDF
2. Find extract/split pages feature
3. Select pages
4. Save as new file

Mobile PDF Tips and Tricks

Tip 1: Use Cloud Storage Wisely

Don't store huge PDFs locally. Your phone's storage fills up fast.

Better approach:

• Keep PDFs in iCloud, Google Drive, or Dropbox
• Download only when needed
• Delete local copies after use

Bonus: Cloud storage means your PDFs are on all your devices.

Tip 2: Compress Before Sending

Mobile data isn't unlimited. Large PDFs eat through your plan.

Before emailing or sharing: Run files through compression first.

25MB → 5MB = 80% less data usage

Your phone bill will thank you.

Tip 3: Save Your Signature

Create your signature once, save it everywhere.

On iPhone:

• Files/Markup saves signatures
• Adobe Reader saves signatures
• Most apps remember your signature

Don't redraw every time. One good signature, reuse forever.

Tip 4: Use Split View on iPad

If you have an iPad:

1. Open PDF in one app
2. Drag to split screen
3. Open notes or email in other half
4. Work on both simultaneously

Great for: Reviewing documents while taking notes or writing emails.

Tip 5: Quick Actions on iPhone

Long-press a PDF in Files:

• Quick Look (preview)
• Markup (annotate)
• Create PDF (from images)
• Print
• Share

No need to open the file first.

Tip 6: Scan to PDF

Both iPhone and Android can scan documents:

iPhone (Notes app):

1. Open Notes
2. Tap camera icon
3. Scan Documents
4. Auto-detects edges
5. Saves as PDF

iPhone (Files app):

1. Open Files
2. Tap three dots → Scan Documents
3. Scan pages
4. Save as PDF

Google Drive (Android):

1. Open Drive
2. Tap + → Scan
3. Capture document
4. Saves as PDF to Drive

Quality is good enough for most documents. For archival quality, use a proper scanner.

Tip 7: Reduce File Size When Scanning

Phone scans default to high resolution. Often too high.

Lower the quality setting when scanning routine documents. You don't need 600 DPI for a receipt.

If the file is still too big: compress it.

Limitations of Mobile PDF Editing

Let's be honest about what mobile can't do well:

Precision Editing

Moving elements pixel-by-pixel is hard on a touchscreen. Fine adjustments are frustrating.

For precise work: Use a computer.

Long Documents

Scrolling through a 200-page PDF on a phone is painful. Navigation is clunky.

For lengthy documents: Better on tablet or desktop.

Complex Forms

Filling out a 10-page form on a phone is tedious. Form fields are tiny. Errors happen.

For complex forms: Desktop is faster and less error-prone.

OCR Quality

Mobile OCR (scanning text from images) is decent but not perfect. Desktop OCR tools (like ABBYY) are better.

For important scans: Consider using PDF Smaller's OCR which works on mobile browsers.

Batch Processing

Processing 50 PDFs one at a time on a phone? No thanks.

For bulk tasks: Desktop all the way.

Best Practices for Mobile PDF Workflows

Do on Mobile

• Quick signatures
• Single-file compression
• Viewing and reviewing
• Simple merges (2-3 files)
• Sharing and sending
• Simple form filling
• Quick scans

Do on Desktop

• Heavy editing
• Batch processing
• Complex form creation
• Precise layout work
• Long document editing
• Advanced OCR needs
• Professional print prep

Hybrid Approach

Often the best workflow combines both:

1. Receive on mobile - Check email, see the PDF
2. Quick review on mobile - Skim content, check it's the right file
3. Note what's needed - "Need to sign page 5, compress, and send back"
4. Simple tasks on mobile - Sign it, compress it
5. Complex tasks on desktop - Major edits can wait

Troubleshooting Mobile PDF Issues

Problem: PDF Won't Open

Possible causes:

• Corrupted file
• Unsupported PDF features
• App limitation

Fixes:

• Try a different app
• Download again (might have been corrupted in transfer)
• Use PDF repair tool if file is damaged

Problem: Can't Find Downloaded PDF

On iPhone: Check Files → Downloads or iCloud Drive

On Android: Check Files app → Downloads folder

Also check: The app you used to download it might store files internally

Problem: Edits Won't Save

Possible causes:

• File is read-only
• Storage is full
• App crashed

Fixes:

• "Save As" to create a new copy
• Free up storage space
• Force-close and reopen app

Problem: PDF Looks Wrong

Possible causes:

• Font substitution (fonts not embedded)
• Screen size limitations
• App rendering issues

Fixes:

• Try different app
• View in browser
• Check on desktop to confirm file isn't actually corrupted

Problem: Signature Looks Terrible

Cause: Drawing with finger on phone is hard

Fixes:

• Use a stylus if you have one
• Practice in a signature app first
• Upload an image of your real signature instead
• Type your name in a script font

Problem: File Too Large to Email

Cause: Attachments over 25MB typically bounce

Fix: Compress the PDF before sending

The Bottom Line

Mobile PDF editing is legitimate. You can handle most everyday PDF tasks from your phone or tablet.

Best approach for most people:

1. Use built-in tools for simple tasks (viewing, basic signing)
2. Use web-based tools like PDF Smaller for compression, merging, conversions
3. Get one good PDF app for more complex needs
4. Save heavy editing for desktop

Don't fight your phone. Quick tasks? Mobile is great. Complex tasks? Wait for your computer.

Our recommendation:

• iPhone users: Built-in Files + PDF Expert for extras + web tools
• Android users: Google Drive + Xodo + web tools
• Both platforms: Bookmark PDF Smaller for compression, merging, and conversions

Ready to work with PDFs on your phone?

Open PDF Smaller on Mobile →

Works on any phone. Any tablet. Any browser.

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Last updated: December 20, 2025