PDF Squeezer vs 4DI
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
PDF Squeezer
Reduce PDF file sizes on your iPhone or iPad with customizable compression settings. Preview changes before saving and process files securely offline. Automate tasks with iOS Shortcuts integration and compress multiple files at once.
- Customizable compression settings
- Preview compressed PDFs
- Offline, on-device processing
- iOS Shortcuts integration
- Batch compression
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PDF Squeezer, the beloved Mac app, is now available for iPhone and iPad! Effortlessly reduce PDF file sizes with customizable compression settings to save space without losing quality. Process files securely on your device, ensuring total privacy with no internet connection required. Experience this well-known app's magic with an unlimited free trial! Customizable Compression Choose from light, moderate, or strong settings to balance file size reduction and quality, right from your iPhone or iPad. See Before You Save Preview your compressed PDFs directly on your device. Ensure the quality meets your needs before saving. Privacy-Focused Compression PDF Squeezer's on-device compression keeps your PDFs private and secure, eliminating the need for an Internet connection. Streamline Your Workflow PDF Squeezer integrates deeply with iOS, including a Shortcuts action for custom workflows. Automate your PDF compression tasks. Batch Compression Compress multiple PDF files at the same time to speed up your work. PDF Squeezer is also available for Mac and Windows as a separate purchase.
4DI
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4DI is an offline reference tool for data integrity in regulated environments — built for QA, validation, manufacturing, and laboratory teams working under GxP. The app organizes data integrity knowledge into five areas: ALCOA++ principles, regulatory frameworks, the data lifecycle, typical inspection findings, and a glossary. ALCOA++ PRINCIPLES 10 principles, each with a clear definition and practical examples contrasting good practice with a typical violation: - Attributable - Legible - Contemporaneous - Original - Accurate - Complete - Consistent - Enduring - Available - Traceable (added per the EMA guideline on computerised systems and electronic data in clinical trials, 2023) REGULATORY FRAMEWORKS 7 frameworks side by side, each with a summary, core requirements, and a link to the official source: - FDA 21 CFR Part 11 - EU GMP Annex 11 - MHRA GxP Data Integrity Guidance - EMA Guideline on computerised systems and electronic data in clinical trials (2023) - PIC/S PI 041 - WHO TRS 1033, Annex 4 — Guideline on data integrity (2021) - ICH Q7 Frameworks are tagged by region (US / EU / International). A comparison view highlights key differences across four topics: audit trail, electronic signatures, risk-based approach, and quality culture & human factors. DATA LIFECYCLE Six phases — Creation, Processing, Review & Approval, Reporting, Retention, Archival & Destruction — each mapped to its relevant ALCOA++ principles, typical pitfalls, and regulatory focus. INSPECTION FINDINGS 17 findings modeled on public patterns from FDA Warning Letters, Form 483 observations, and EU GMP non-conformities. Organized by category and severity, each finding lists the principles violated, its regulatory basis, and remediation measures, with links to official databases. Full search included. GLOSSARY 29 terms — ALCOA terms, regulatory abbreviations (CFR, GMP, GLP, GCP...), technical terms (audit trail, metadata, electronic signature), and quality terms (CAPA, deviation, OOS) — each with a definition and context. Bookmark terms for quick access, get a "term of the day," and search even without typing accents. FIVE LANGUAGES 4DI speaks English, German, French, Spanish and Italian. A new installation starts in your iPhone's language when 4DI supports it. You can switch the language any time in the app's Settings. MADE FOR IPHONE DUO Half open, one half holds the definition or finding you picked while the other lets you browse and compare; fully open, list and details sit side by side like a book. BUILT FOR OFFLINE USE Light, dark, or system appearance. Works entirely offline: no accounts, no tracking, no ads, no permissions required. Bookmarks stay on your device. COMMUNITY & SUPPORT Report a bug, suggest a feature, or flag a content correction through the app's Settings — linked to robspace's public GitHub hub for discussion. For direct support: support@robspace.de. DISCLAIMER: 4DI is a privately developed helping tool. It is not endorsed, certified, or validated by any regulatory authority. Content is for informational purposes only and must not replace official regulatory guidance or professional advice.
Screenshots
Verdict
The clearest difference is in-app purchases: 4DI at none against PDF Squeezer's 1. 4DI also leads on update cadence (weekly vs monthly). 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
Both are free to download. PDF Squeezer sells 1 one-off in-app purchase. 4DI asks for nothing beyond the download.
PDF Squeezer ships an update monthly, 4DI weekly. The most recent releases landed on October 27, 2026 and October 25, 2026 respectively.
| Parameter | PDF Squeezer | 4DI |
|---|---|---|
| Price | Free | Free |
| Rating | 4.8 (22 ratings) — better | — |
| Positive reviews | 63.6% of reviews | — |
| Number of ratings | 22 — better | — |
| Update frequency | Monthly | Weekly — better |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | — |
| Devices | iPhone, iPad — better | iPhone |
| Requires iOS | 17.0 — better | 18.6 |
| Further details — not scored | ||
| Size | 29 MB | 5 MB |
| Age rating | 4+ | 4+ |
| Developer | Daniel Witt | Robert Poetzsch |
In-app purchases
PDF Squeezer
- Full Version$9.99
4DI
No in-app purchases









