# How to Chat With a PDF on iPhone and Check the Answers

> Ask questions about a PDF on iPhone with ChatGPT, Claude, Gemini Notebook, ChatPDF or SumAI. How to phrase questions, verify answers and work within limits.

- Source: https://getsumai.app/blog/how-to-chat-with-a-pdf-on-iphone/
- Last updated: 2026-11-12
- About: SumAI: YouTube & PDF Summary, an AI summarizer app for iPhone and iPad

## Key takeaways

- Chatting with a PDF means asking questions in plain language and getting answers drawn from the text of that document.
- On iPhone the main options are ChatGPT, Claude, Gemini, Gemini Notebook, ChatPDF, Acrobat's AI Assistant and SumAI's Ask AI.
- Specific, single questions that ask where the document says something are the easiest to answer and to check.
- Documented limits vary as of November 2026: Claude accepts PDFs of up to 1,000 pages but reads charts only up to 100 pages, and ChatGPT's free plan allows 3 file uploads a day.
- Verify an important answer by finding the passage, reading the sentences around it and comparing numbers, names and dates exactly.

## Quick steps: How to ask questions about a PDF on iPhone with SumAI

1. **Summarize the PDF first.** Open SumAI, start a new summary and choose the PDF from your files. The PDF needs selectable text. Pick a summary style and a language.
2. **Read the summary.** Skim the summary to see what the document covers and which terms it uses, so you know what to ask.
3. **Ask one specific question in Ask AI.** Open **Ask AI** and type a question about one thing, such as a definition, a figure or a step. Ask which section the answer comes from.
4. **Check the answer in the PDF.** Search the PDF for the phrase or figure, and read the sentences around it before you rely on the answer.

To ask questions about a PDF on an iPhone, open the document in an app that reads its text and answers from it. The main options are a general assistant (ChatGPT, Claude or Gemini), Gemini Notebook (formerly NotebookLM), a PDF chat tool such as ChatPDF or Acrobat's AI Assistant, and SumAI's Ask AI. Ask one specific question at a time, then check important answers against the page.

SumAI is our app, so weigh our view accordingly. Facts about other products come from their makers' help pages and App Store listings, checked in November 2026. Prices and limits change.

## What does it mean to chat with a PDF?

Chatting with a PDF means asking questions in plain language and getting answers drawn from the text of that document, not from whatever an AI model happens to know about the topic. You might ask which sample size a study used, how a manual says to reset a device, or how a textbook chapter defines a term.

Two things follow. The tool can only use text it can read, so a scanned page or a chart may be invisible to it. And the answer is still written by a language model, which can misread a passage or state a detail the document does not contain. Treat each answer as a pointer to the right passage, then read the passage.

## Which apps let you ask questions about a PDF on iPhone?

As of November 2026, these are the main options with an iPhone app:

- **ChatGPT, Claude and Gemini.** Attach the PDF to a chat and ask. These general assistants answer document questions in the same chat as everything else, within the upload limits listed further down.
- **Gemini Notebook.** Add the PDF to a notebook as a source. [Google's help page](https://support.google.com/gemininotebook/answer/16296687?hl=en&co=GENIE.Platform%3DiOS) says the iPhone app accepts PDFs, and the [App Store listing](https://apps.apple.com/us/app/gemini-notebook/id6737527615) says answers cite your sources in-line.
- **ChatPDF.** [ChatPDF's site](https://www.chatpdf.com/) says answers carry clickable citations that scroll to the source passage, and that the free plan covers 2 documents a day. The [App Store listing](https://apps.apple.com/us/app/chatpdf-chat-pdf-ai/id6742454061) shows the iPhone app was last updated in May 2025.
- **Adobe Acrobat AI Assistant.** Acrobat Reader's [App Store listing](https://apps.apple.com/us/app/acrobat-reader-pdf-editor/id469337564) describes cited answers about your PDFs. [Adobe's requirements page](https://helpx.adobe.com/acrobat/desktop/use-acrobat-ai/get-started-with-generative-ai/ai-tech-requirements.html) limits it to PDFs under 100 MB and up to 600 pages, and to prompts under 500 characters.
- **Siri AI (beta).** On iOS 27 with a supported iPhone, Apple says you can [ask Siri about content on your screen](https://support.apple.com/guide/iphone/get-started-with-siri-ai-iphv6zwrg8jvfgr/ios), such as a PDF. Siri AI is not initially available in the EU on iOS.
- **SumAI.** After SumAI summarizes a PDF, [Ask AI](https://getsumai.app/features/ask-ai-chat/) answers questions from the text of that document, next to the summary, mind map, quiz and flashcards.

## How do you ask good questions about a PDF?

Good questions about a PDF are narrow enough that you can check the answer. Four habits help:

1. **Be specific.** Name the section, term or figure you mean. Asking what section 4 says about battery replacement works better than asking about the battery.
2. **Ask one thing at a time.** A question with three parts is harder to answer completely and harder to check.
3. **Ask where the document says it.** Request the section heading and a short phrase from the passage, so you can find it yourself.
4. **Ask for the exact figure, then check it.** Numbers, dates, names and units are where a wrong detail does the most damage.

Example questions for four common goals:

| Goal | Example question | What to check |
|---|---|---|
| Understand | Explain the main argument of chapter 2 in three sentences, using the document's own terms. | The terms and the order of the argument |
| Find | What sample size did the study use, and in which section is it stated? | The number, in that section |
| Compare | How do the two methods in section 5 differ? List only differences the document states. | Each difference against section 5 |
| Study | Ask me five questions about chapter 4, one at a time, and say which part of the chapter each answer comes from. | Your answers against the chapter |

## How do you verify an answer from a PDF?

Verifying an answer from a PDF takes four steps:

1. **Find the passage.** In Gemini Notebook, ChatPDF and Acrobat's AI Assistant, follow the citation. In other tools, ask for the section and a short phrase, then search the PDF. In Apple's Preview app, [tap the Search button and enter a word or phrase](https://support.apple.com/guide/iphone/open-and-view-pdfs-and-images-iph7a0cdad0c/ios).
2. **Read the sentences around it.** Check that the passage says what the answer says, including conditions such as "only", "up to" or "in this sample".
3. **Compare figures character by character.** Check numbers, units, dates and names.
4. **Check the scope.** A [2025 study in Royal Society Open Science](https://doi.org/10.1098/rsos.241776) analyzed 4,900 AI summaries of scientific texts and found that most of the 10 models tested stated findings more broadly than the originals did. If an answer sounds general, ask what the finding is limited to.

If you cannot find a supporting passage, treat the answer as unconfirmed. When you need to quote the document, copy the words from the PDF, not from the chat. [How accurate are AI summaries?](https://getsumai.app/blog/how-accurate-are-ai-summaries/) covers the research in more detail.

## What are the limits of chatting with a PDF?

### Scanned PDFs

A scanned PDF is a set of page images, so a tool that reads the text layer has nothing to work with. SumAI needs a PDF with selectable text. If you cannot select or search any words in the file, it is a scan and needs OCR first.

ChatPDF's [summary page](https://www.chatpdf.com/pdf-summary) says it supports scanned PDFs. [How to summarize a PDF on iPhone](https://getsumai.app/blog/how-to-summarize-a-pdf-on-iphone/) explains the check and the options.

### Charts, figures and images

Tools that work from text do not read information that exists only in a chart or image, and that includes SumAI. For a question about a chart, look at the chart yourself.

Some tools do read images. OpenAI says ChatGPT can analyze both the text and the images in a PDF, including charts and diagrams. Anthropic says Claude reads visual elements only in PDFs of 100 pages or fewer. Adobe's requirements page says AI Assistant does not support images or complex vector graphics, although its App Store listing mentions answers about charts, graphs and tables.

### Long documents

Documented limits for long PDFs, as of November 2026:

- **Claude:** PDFs of up to 1,000 pages, per [Anthropic's upload guide](https://support.claude.com/en/articles/8241126-upload-files-to-claude).
- **ChatGPT:** up to 512 MB per file, and 3 file uploads a day on the free plan, per [OpenAI's upload guide](https://help.openai.com/en/articles/8555545-uploading-files-and-audio-to-chatgpt). OpenAI's [pricing page](https://chatgpt.com/pricing/) also lists an input maximum of about 12 pages of text for the free plan's GPT Instant model. We could not confirm how that figure applies to a long uploaded PDF.
- **Gemini:** a context window of 32,000 tokens without a paid plan, 128,000 on AI Plus and 1 million on AI Pro and AI Ultra. [Google describes](https://support.google.com/gemini/answer/16275805?hl=en) the context window as how much content can be understood together at one time.
- **Gemini Notebook:** up to 500,000 words or 200 MB per source, with no page limit, per [its FAQ](https://support.google.com/notebooklm/answer/16269187).

A simple test works in any tool: ask about a detail you know is near the end of the document. If the answer misses it, do not rely on that chat for the later sections.

## How do you ask questions about a PDF with SumAI?

In SumAI, a chat starts from a summary. Pick the PDF, choose a summary style and a language, and read the summary first. It shows what the document covers and which terms it uses, which makes your questions sharper.

Then open Ask AI and type a question. SumAI answers from the text of that document.

For videos, Ask AI answers include timestamps you can tap. A PDF has no timestamps, so build the check into the question: ask which section the answer comes from, and for a short phrase you can search for. When you are studying, follow the chat with the [quiz and flashcards](https://getsumai.app/features/flashcards-and-quizzes/) that SumAI generates from the summary.

The limits are plain. SumAI's [PDF summarizer](https://getsumai.app/features/pdf-summarizer/) needs a PDF with selectable text, and like any AI answer, an Ask AI answer can miss nuance or get a detail wrong, so the checks above apply to SumAI too. SumAI is an iPhone and iPad app, with no Android app, web app or browser extension. It is free to download, with an optional Premium subscription.

## What should you check before relying on an answer?

- The PDF has selectable text. If you cannot select or search any words, it is a scan.
- You asked one specific question.
- You found the passage and read the sentences around it.
- Figures, names and dates match the PDF exactly.
- The answer is no broader than the passage.
- Anything you quote is copied from the PDF, not from the chat.

For a medical, legal or financial decision, read the relevant part of the document itself. A chat can show you where to look.

## Frequently asked questions

### Can I chat with a PDF on iPhone for free?

Yes, within limits. As of November 2026, ChatGPT's free plan allows 3 file uploads a day, ChatPDF's free plan covers 2 documents a day, and Gemini Notebook is free with a Google Account. SumAI is free to download, with an optional Premium subscription. Free allowances change, so check each app before you depend on it.

### What is the best AI to chat with a PDF?

It depends on what you need. For answers that point to the exact passage, Gemini Notebook, ChatPDF and Acrobat's AI Assistant show citations. For charts, OpenAI says ChatGPT analyzes images inside PDFs. For studying, SumAI adds a summary, a quiz and flashcards to its Ask AI chat. No tool removes the need to check important answers.

### Can ChatGPT read a whole PDF?

OpenAI's upload guide allows files up to 512 MB and caps text and document files at 2 million tokens. Its pricing page also lists an input maximum of about 12 pages of text for the free plan's GPT Instant model. We could not confirm how that applies to long PDFs, so test with a question about a late section.

### Can AI answer questions about a scanned PDF?

Only if the tool can turn the page images into text. SumAI needs a PDF with selectable text. ChatPDF says it supports scanned PDFs. If you cannot select or search any words in the file, it is a scan: run it through an OCR tool that saves a searchable PDF, then ask your questions.

### Can I chat with a PDF in SumAI?

Yes. Ask AI works with documents as well as videos. Open a PDF you have summarized in SumAI, type a question, and SumAI answers from the text of that document. The PDF needs selectable text. To check an answer, ask which section it comes from and look it up in the PDF.

### How do I know if an AI answer about my PDF is correct?

Find the passage the answer is based on and read the sentences around it. Follow the citation if the tool gives one, or ask for the section and a short phrase and search the PDF. Then compare numbers, names and dates exactly. If you cannot find a supporting passage, treat the answer as unconfirmed.

## Sources

- [Uploading files and audio to ChatGPT](https://help.openai.com/en/articles/8555545-uploading-files-and-audio-to-chatgpt), OpenAI Help Center
- [ChatGPT pricing](https://chatgpt.com/pricing/), OpenAI
- [Upload files to Claude](https://support.claude.com/en/articles/8241126-upload-files-to-claude), Claude Help Center (Anthropic)
- [Gemini Apps limits & feature availability](https://support.google.com/gemini/answer/16275805?hl=en), Gemini Apps Help
- [NotebookLM is now Gemini Notebook](https://blog.google/innovation-and-ai/products/gemini-notebook/notebooklm-gemini-notebook/), Google
- [Get started with the Gemini Notebook mobile app (iPhone & iPad)](https://support.google.com/gemininotebook/answer/16296687?hl=en&co=GENIE.Platform%3DiOS), Gemini Notebook Help
- [Learn about Gemini Notebook's plans](https://support.google.com/gemininotebook/answer/16213268), Gemini Notebook Help
- [Frequently asked questions](https://support.google.com/notebooklm/answer/16269187), Gemini Notebook Help
- [Gemini Notebook (App Store listing)](https://apps.apple.com/us/app/gemini-notebook/id6737527615), Apple App Store
- [ChatPDF](https://www.chatpdf.com/), ChatPDF
- [PDF Summary](https://www.chatpdf.com/pdf-summary), ChatPDF
- [ChatPDF - Chat PDF AI (App Store listing)](https://apps.apple.com/us/app/chatpdf-chat-pdf-ai/id6742454061), Apple App Store
- [Generative AI technical requirements in Acrobat](https://helpx.adobe.com/acrobat/desktop/use-acrobat-ai/get-started-with-generative-ai/ai-tech-requirements.html), Adobe Help Center
- [Acrobat Reader: PDF Editor (App Store listing)](https://apps.apple.com/us/app/acrobat-reader-pdf-editor/id469337564), Apple App Store
- [Get started with Siri AI on iPhone](https://support.apple.com/guide/iphone/get-started-with-siri-ai-iphv6zwrg8jvfgr/ios), Apple Support (iPhone User Guide)
- [Open and view PDFs and images in Preview on iPhone](https://support.apple.com/guide/iphone/open-and-view-pdfs-and-images-iph7a0cdad0c/ios), Apple Support (iPhone User Guide)
- [Generalization bias in large language model summarization of scientific research (Peters and Chin-Yee, 2025)](https://doi.org/10.1098/rsos.241776), Royal Society Open Science