# OPAS Calendar vs PDF Viewer by Nutrient

The clearest difference is review sentiment: PDF Viewer by Nutrient at 73% against OPAS Calendar's 0%. PDF Viewer by Nutrient also leads on rating (4.6 vs 1.7) and ratings volume (9.1K vs 7). OPAS Calendar's advantage is in-app purchases (none vs 2) and iOS requirement (11.0 vs 17.0). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. PDF Viewer by Nutrient sells 2 in-app purchases, starting at $6.99 per 3 months. OPAS Calendar asks for nothing beyond the download.

PDF Viewer by Nutrient holds the better App Store score, 4.6 against 1.7. That said, the two scores are not equally well evidenced: PDF Viewer by Nutrient has 9.1K ratings behind it against 7, so its average is the more settled of the two. Written reviews point the same way: 0% of OPAS Calendar's written reviews are positive against 73% of PDF Viewer by Nutrient's.

Both ship on a similar rhythm, roughly monthly. The most recent releases landed on October 24, 2026 and October 27, 2026 respectively.

## The numbers

| Metric | OPAS Calendar | PDF Viewer by Nutrient |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [1.7 (7 ratings)](https://appshunter.io/ios/app/opas-calendar/id898227192/reviews) | **[4.6 (9.1K ratings)](https://appshunter.io/ios/app/pdf-viewer-by-nutrient/id1120099014/reviews)** |
| Number of ratings | 7 | **9.1K** |
| Positive reviews | 0.0% of reviews | **73.3% of reviews** |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Monthly | Monthly |
| Monetization | **Free** | Freemium |
| Size | 9 MB | 109 MB |
| Requires iOS | **11.0** | 17.0 |
| Devices | iPhone, iPad, iPod | **iPhone, iPad, Mac, Vision Pro** |
| Age rating | 4+ | 4+ |
| Developer | [OPAS Software GmbH](https://appshunter.io/developer/1704978541) | [PSPDFKit GmbH](https://appshunter.io/developer/966931428) |

## What reviewers say

### OPAS Calendar

[App page](https://appshunter.io/ios/app/opas-calendar/id898227192)

This application syncs with the OPAS online system to display your orchestra planning and administration dates on your mobile device. It requires an existing OPAS software license and online access to function.

**Highlights:** View OPAS dates on mobile, Syncs with OPAS online system, Requires OPAS software, Orchestra planning tool

**Features:** macOS Compatibility

**In-app purchases:** none


### PDF Viewer by Nutrient

[App page](https://appshunter.io/ios/app/pdf-viewer-by-nutrient/id1120099014)

Easily view, search, and annotate PDF documents on your iPhone and iPad. Import files from cloud services, fill out forms, add signatures, and organize your documents. Advanced features like redaction and combining documents are available with a Pro subscription.

**Highlights:** View and search PDFs, Annotate with highlights and notes, Sign documents digitally, Fill out PDF forms, Organize and share documents, Import from cloud services

**Features:** Family Sharing, iMessage stickers

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| PDF Viewer Pro 3 Months | $6.99 | per 3 months |
| PDF Viewer Pro Yearly | $19.99 | per year |

**What reviewers like**

- 🚀 Seamless integration with iCloud and Files app
- 👍 Intuitive annotation tools with Apple Pencil
- 🎨 Versatile highlighting and drawing options
- 💾 Saves annotations to original PDF files
- 🔍 Powerful search and navigation features

**What reviewers complain about**

- 🐛 Occasional crashes and performance issues
- 🤔 Confusing UI and steep learning curve
- 🔀 Difficulty managing and organizing PDF files
- 🔍 Inconsistent text selection and highlighting
- 🔒 Privacy concerns around data collection

**Reported bugs**

- Annotations randomly disappearing or not saving
- Incompatibility issues with certain PDF files
- Scrolling and panning problems on large PDFs
- Unexpected crashes after iOS updates

**Requested features**

- Add a rubber/eraser tool for annotations
- Implement a side-by-side PDF view mode
- Improve palm rejection and gesture support
- Allow customization of toolbar and shortcuts
- Provide better options for PDF file management


## Frequently asked questions

### Is OPAS Calendar free?

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

### Is PDF Viewer by Nutrient free?

PDF Viewer by Nutrient is free to download, with in-app purchases available.

### Which has better reviews, OPAS Calendar or PDF Viewer by Nutrient?

PDF Viewer by Nutrient is rated higher. OPAS Calendar averages 1.7 out of 5 from 7 ratings, while PDF Viewer by Nutrient averages 4.6 from 9.1K ratings.

### Do OPAS Calendar or PDF Viewer by Nutrient have ads?

Neither OPAS Calendar nor PDF Viewer by Nutrient shows ads.

### Which is updated more often, OPAS Calendar or PDF Viewer by Nutrient?

OPAS Calendar ships an update monthly, and PDF Viewer by Nutrient monthly. Most recently, OPAS Calendar was updated on October 24, 2026 and PDF Viewer by Nutrient on October 27, 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.*