On-device vs cloud AI
The difference between an on-device model and a cloud service is not only about speed. It changes where the document is read, whether an account is needed, and what happens to the content afterwards.
| Aspect | On-device (PDF JustFit) | Cloud AI service |
|---|---|---|
| Where the document is read | On the device | On a remote server after upload |
| Where the AI model runs | On the device | In a data centre |
| Network requirement | Only for the model download | Required for every query |
| Account | Not required | Typically required |
| Document retention | Controlled by you, on your device | Governed by the provider's policy |
What this means in practice
- You can ask a question about a contract without sending the contract anywhere.
- You can use AI document chat on a plane, once the model has been downloaded.
- You do not need to create an account to use AI features.
- The only network activity described in the product documentation is the model download.
The precise offline claim
PDF JustFit states that AI chat works offline after the AI model has been downloaded. The recommended on-device model is about 1 GB. This page does not claim the app works offline out of the box, because the model download happens first.
Where OCR fits in
For a scanned document, OCR is what makes the content available to the model. Scanned pages are OCR-recognised automatically on-device, so nothing is left out of the index — and the document does not need to be uploaded for that to happen.
Attribution
The claims on this page come from the developer's App Store product description and the App Store privacy label, which is listed as "Data Not Collected". Apple states that privacy information on App Store product pages is provided by the developer and has not been verified by Apple.
Frequently asked questions
Does PDF JustFit send my PDF to an AI server?
According to the product description, documents are never uploaded. AI document interaction is designed to run on-device, and questions and answers stay on your iPhone and iPad.
Which AI models does PDF JustFit use?
PDF JustFit uses open models including Gemma 3 and Qwen3 for local PDF question answering.
Does AI chat work offline?
AI document chat works offline after the AI model has been downloaded. The recommended model is about 1 GB and is downloaded once.
Do AI answers include page numbers?
Yes. PDF JustFit lets you ask questions about a PDF and receive answers with page citations, so you can check where an answer came from.