Comparison

Smart PDF Compressor vs PDF Under

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

PDF Under

Features
Read full description

Your PDF is ready. Then the upload form says: file too large. Maybe it needs to be under 10 MB. Or 2 MB. Or even 500 KB. You don't want to learn compression settings, and you definitely don't want to keep guessing—compress, check the size, try again, compress again. You just need the PDF to fit. That's what PDF Under is built for. Tell it the MB or KB you need, and it works toward exactly that number. But making a PDF smaller is only half the problem. It still has to look like your PDF. Some compression methods shrink a file by turning every page into a picture—smaller, yes, but the text is no longer selectable, and the document never quite looks right again. PDF Under does it differently. Whenever possible, it keeps your text and vector content untouched, and compresses only the embedded images that were taking up the space in the first place. Smaller file. Same document. You choose the number. 500 KB, 1 MB, 2 MB, 5 MB, 10 MB, or a custom target of your own—no "low, medium, high" guessing games, just the size you were actually asked for. And before you save or share anything, you see the result first: the final size, the finished pages, exactly what you're about to send. Where does this happen? On your phone. Not on a server somewhere. Your PDF is never uploaded, which matters more than usual when the document you're shrinking is the one you'd rather not hand to a random compression website in the first place. No account. No sign-in. Just your file, compressed, still yours. Now, the honest part. Not every target is reachable. A fifty-page scanned document doesn't become 500 KB without something giving—that's just how file size and image quality work, and PDF Under won't pretend otherwise. When your target is more aggressive than the document can survive, it tells you plainly, shows you the smallest version that's still readable, and lets you decide from there. No silent damage. No surprises when you open the file later. This is the app for the moment a portal, a form, an inbox, or a government website hands you a number and expects you to hit it—job applications, school submissions, legal filings, an email that keeps bouncing back because the attachment is too big. Select the PDF, set the target, compress, check the result, send it. Five steps, and you're done. PDF Under is free to try—your first three compressions cost nothing. After that, a Weekly, Yearly, or Lifetime plan unlocks unlimited use, so you're never stuck mid-deadline wondering if today's the day you run out. Subscriptions renew automatically unless canceled at least 24 hours before the current period ends, and you can manage or cancel anytime in your Apple Account settings. Full pricing is shown in the app before you're asked to pay anything. Because when a website tells you your PDF is too large, you shouldn't have to become a compression expert just to send a document. You should just be able to get it under the limit. By downloading, you agree to the Standard Apple End User License Agreement: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

Smart PDF Compressor4 screens
PDF Under4 screens

Verdict

The call

The clearest difference is in-app purchases: Smart PDF Compressor at none against PDF Under's 3. Smart PDF Compressor also leads on update cadence (every 9 days vs every 3 weeks). On price, ads, device support and iOS requirement there is nothing between them.

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

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. PDF Under sells 3 in-app purchases, starting at $1.99 per 7 days. Smart PDF Compressor asks for nothing beyond the download.

UpkeepUpdate frequency

Smart PDF Compressor ships an update every 9 days, PDF Under every 3 weeks. The most recent releases landed on October 31, 2026 and October 25, 2026 respectively.

Scorecard2 real differences · 4 level
Smart PDF Compressor versus PDF Under: the parameters behind the verdict, then further details
ParameterSmart PDF CompressorPDF Under
PriceFreeFree
Update frequencyEvery 9 days — betterEvery 3 weeks
AdsNoNo
In-app purchasesNo — betterYes
DevicesiPhone, iPad — betteriPhone
Requires iOS18.017.6 — better
Further details — not scored
Size4 MB3 MB
Age rating4+4+
DeveloperQuan DangEmre KABOGLU

In-app purchases

None

Smart PDF Compressor

No in-app purchases

3 purchases

PDF Under

Subscriptions2
  • PDF Under Weekly$1.997 Days
  • PDF Under Yearly$13.991 Year
One-time1
  • PDF Under Lifetime$19.99

Questions

Is Smart PDF Compressor free?
Smart PDF Compressor is free to download, with no in-app purchases.
Is PDF Under free?
PDF Under is free to download, with in-app purchases available.
Do Smart PDF Compressor or PDF Under have ads?
Neither Smart PDF Compressor nor PDF Under shows ads.
Which is updated more often, Smart PDF Compressor or PDF Under?
Smart PDF Compressor ships an update every 9 days, and PDF Under every 3 weeks. Most recently, Smart PDF Compressor was updated on October 31, 2026 and PDF Under on October 25, 2026.

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