Comparison

Smart PDF Compressor vs UnderLimit

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Smart PDF Compressor

Features
Read full description

Smart PDF Compressor is a free, offline PDF compressor for iPhone and iPad that helps anyone emailing, uploading or storing a PDF dramatically reduce file size (for example, shrinking an 8-page scan from 5.6 MB to 669 KB, 88.1% smaller) — without the file ever leaving the device. ALL PROCESSING IS LOCAL Your documents never leave your device. No internet connection required, no cloud uploads, no data collection. Complete privacy guaranteed. KEY FEATURES - Target Size Mode: Pick an exact target file size (25 MB, 10 MB, 5 MB, 2 MB, or custom) to fit email and upload limits - Keep Text & Links Selectable: Preserves original text, hyperlinks, and document structure by default - Size Estimates First: See the estimated size for each option before you compress - Three Presets: Best quality, Balanced (recommended) and Smallest file - Advanced Options: 1-bit black & white mode, optional OCR text recognition, resolution override (72–300 DPI), and metadata removal - Smart Compression: Automatically detects scanned vs. digital pages and applies suitable settings - Batch Compression: Compress multiple PDFs at once with progress tracking - Share as ZIP: Bundle several compressed PDFs into one ZIP archive and name it before you share - Side-by-Side Preview: Compare original and compressed pages before saving - File History: Browse, preview, rename, and share all your compressed files - Appearance & Languages: Light/Dark mode and support for English, German, French, Japanese, and Korean - Works on iPhone and iPad HOW IT WORKS 1. Tap Choose PDF and pick a file from Files 2. Choose a preset or set a target size — see estimated results before compressing 3. Tap Compress PDF and see the exact before and after sizes 4. Share or save your compressed PDF, or send several as one ZIP PERFECT FOR - Reducing email attachment sizes - Fitting strict upload limits on portals and government forms - Saving storage space on your device - Compressing scanned receipts, contracts, and books - Preparing files for sharing via messaging apps Smart PDF Compressor uses advanced on-device image processing and structure-preserving optimization to deliver fast, reliable compression without sacrificing readability.

About

UnderLimit

Features
Read full description

Make your files fit the limit. UnderLimit helps you reduce photos and PDFs to the file size you actually need. Choose your target size, and UnderLimit handles the compression while preserving the best quality possible. PERFECT FOR FILE SIZE LIMITS Need a photo under 1 MB? A PDF under 5 MB? An attachment small enough to upload or send? Set the target size and let UnderLimit do the work. PHOTO COMPRESSION • Compress photos to a target file size • Reduce image size in KB or MB • Keep the best quality possible • Quickly prepare images for uploads, forms, email, and sharing PDF COMPRESSION • Reduce PDF file size • Choose the maximum size you need • Prepare PDFs for upload limits and attachments • Simple, fast workflow SMART RECOMMENDATIONS Not sure which target size to choose? UnderLimit can help you select an appropriate size for your file. PRIVATE BY DESIGN Your files are processed directly on your device. Your photos and PDFs don't need to be uploaded to a remote server for compression. SIMPLE PRICING Start using UnderLimit for free. If you need more, unlock UnderLimit Unlimited with a one-time purchase. No subscription. No ads. No account required. UNDERLIMIT IS USEFUL FOR • Online forms and portals • Email attachments • Applications and document submissions • Websites with maximum upload sizes • Reducing photos before sharing • Compressing PDFs for size-restricted uploads Stop guessing compression levels. Choose the size you need and make your file fit the limit.

Screenshots

Smart PDF Compressor4 screens
UnderLimit4 screens

Verdict

The call

The clearest difference is in-app purchases: Smart PDF Compressor at none against UnderLimit's 1. UnderLimit's advantage is update cadence (every 2 days vs every 9 days). On price, ads, device support and iOS requirement there is nothing between them.

Scored on Price Ā· Rating Ā· Positive reviews Ā· Number of ratings Ā· Update frequency Ā· Ads Ā· In-app purchases Ā· Monetization Ā· Best chart rank Ā· Devices Ā· Requires iOS

CostPrice Ā· In-app purchases Ā· Ads Ā· Monetization

Both are free to download. UnderLimit sells 1 one-off in-app purchase. Smart PDF Compressor asks for nothing beyond the download.

UpkeepUpdate frequency

Smart PDF Compressor ships an update every 9 days, UnderLimit every 2 days. The most recent releases landed on November 9, 2026 and November 6, 2026 respectively.

Scorecard2 real differences Ā· 4 level
Smart PDF Compressor versus UnderLimit: the parameters behind the verdict, then further details
ParameterSmart PDF CompressorUnderLimit
PriceFreeFree
Update frequencyEvery 9 daysEvery 2 days — better
AdsNoNo
In-app purchasesNo — betterYes
DevicesiPhone, iPadiPhone, iPad
Requires iOS18.017.0 — better
Further details — not scored
Size4 MB4 MB
Age rating4+4+
DeveloperQuan DangALESSANDRO VINCENZO DEL BALZO

In-app purchases

None

Smart PDF Compressor

No in-app purchases

1 purchases

UnderLimit

One-time1
  • UnderLimit Unlimited$2.99

Questions

Is Smart PDF Compressor free?
Smart PDF Compressor is free to download, with no in-app purchases.
Is UnderLimit free?
UnderLimit is free to download, with in-app purchases available.
Do Smart PDF Compressor or UnderLimit have ads?
Neither Smart PDF Compressor nor UnderLimit shows ads.
Which is updated more often, Smart PDF Compressor or UnderLimit?
Smart PDF Compressor ships an update every 9 days, and UnderLimit every 2 days. Most recently, Smart PDF Compressor was updated on November 9, 2026 and UnderLimit on November 6, 2026.

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