# ISS calculator vs PDF Compressor

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

Both are free to download. PDF Compressor sells 3 in-app purchases, starting at $2.99 per month. ISS calculator asks for nothing beyond the download.

ISS calculator ships an update every 3 days, PDF Compressor every 3 weeks. The most recent releases landed on September 22, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | ISS calculator | PDF Compressor |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/iss-calculator/id1531086115/reviews)** | — |
| Number of ratings | **1** | — |
| In-app purchases | **No** | Yes |
| Ads | **No** | Yes |
| Update frequency | **Every 3 days** | Every 3 weeks |
| Monetization | Free | — |
| Size | 2 MB | 31 MB |
| Requires iOS | **13.0** | 16.2 |
| Devices | iPhone, iPod | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Sujal Adhia](https://appshunter.io/developer/1475334795) | [Swetha MB](https://appshunter.io/developer/599426588) |

## What reviewers say

### ISS calculator

[App page](https://appshunter.io/ios/app/iss-calculator/id1531086115)

This tool helps assess the severity and extent of ichthyosis across the body. It's designed for clinical trials, research, and practice to track treatment response in adults and children. The system follows FDA guidelines for comprehensive scoring.

**Highlights:** Assess ichthyosis extent and severity, User-friendly instrument, For clinical trials and research, Track treatment response, Score adults and children, Follows FDA guidelines

**Features:** macOS Compatibility

**In-app purchases:** none


### PDF Compressor

[App page](https://appshunter.io/ios/app/pdf-compressor-editor-and-tools/id6756212575)

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

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Unlock All Photo PDF functionality | $2.99 | per month |
| Unlock All Photo PDF functionality | $9.99 | per 6 months |
| Unlock All Photo PDF functionality | $14.99 | per year |


## Frequently asked questions

### Is ISS calculator free?

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

### Is PDF Compressor free?

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

### Do ISS calculator or PDF Compressor have ads?

PDF Compressor shows ads; ISS calculator does not.

### Which is updated more often, ISS calculator or PDF Compressor?

ISS calculator ships an update every 3 days, and PDF Compressor every 3 weeks. Most recently, ISS calculator was updated on September 22, 2026 and PDF Compressor on October 25, 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.*