# PDF Slim vs UnderMB

The clearest difference is in-app purchases: UnderMB at none against PDF Slim's 1. On price, rating, ratings volume and update cadence there is nothing between them.

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

On the App Store both sit at effectively the same score — 5.0 for PDF Slim against 5.0 for UnderMB. Both are backed by a comparable volume of ratings — 1 and 1 respectively.

PDF Slim ships an update weekly, UnderMB every 11 days. The most recent releases landed on November 10, 2026 and October 31, 2026 respectively.

## The numbers

| Metric | PDF Slim | UnderMB |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [5.0 (1 ratings)](https://appshunter.io/ios/app/pdf-slim-reduce-pdf-size/id6787603119/reviews) | [5.0 (1 ratings)](https://appshunter.io/ios/app/undermb-file-size-compressor/id6811049521/reviews) |
| Number of ratings | 1 | 1 |
| In-app purchases | Yes | **No** |
| Ads | Yes | Yes |
| Update frequency | **Weekly** | Every 11 days |
| Monetization | Ad-supported | Ad-supported |
| Size | 14 MB | 9 MB |
| Requires iOS | 15.0 | 15.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [MBG Studio](https://appshunter.io/developer/1401126212) | [CEMRE SIMSEK](https://appshunter.io/developer/6801148028) |

## What reviewers say

### PDF Slim

[App page](https://appshunter.io/ios/app/pdf-slim-reduce-pdf-size/id6787603119)

Reduce the size of your PDF files with adjustable quality settings. Save or share compressed documents directly from the application. Access detailed information about each PDF.

**Highlights:** Compress PDF files, Adjustable quality levels, Save compressed PDFs, Share instantly, View PDF details

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Remove Ads | $0.99 | one-time |


### UnderMB

[App page](https://appshunter.io/ios/app/undermb-file-size-compressor/id6811049521)

Reduce the size of photos, videos, audio, and PDFs on your device. Select a target file size or use presets for common uploads like email or chat apps. Preview your compressed files before saving or sharing, with optional metadata removal.

**Highlights:** Compress images, videos, audio, and PDFs, Choose target file size (KB/MB), Built-in presets for uploads, Preview before saving, Optional metadata removal, Batch processing

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is PDF Slim free?

PDF Slim is free to download, with in-app purchases available.

### Is UnderMB free?

UnderMB is free to download, with no in-app purchases.

### Which has better reviews, PDF Slim or UnderMB?

PDF Slim and UnderMB are both rated 5.0 out of 5 on the App Store, from 1 and 1 ratings respectively.

### Do PDF Slim or UnderMB have ads?

Both PDF Slim and UnderMB show ads.

### Which is updated more often, PDF Slim or UnderMB?

PDF Slim ships an update weekly, and UnderMB every 11 days. Most recently, PDF Slim was updated on November 10, 2026 and UnderMB on October 31, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*