How to Analyze PDFs and Long Documents with AI (Claude, Gemini and ChatGPT)

The tool you choose depends mainly on your document size and how many files you want to analyze together:

Tool	Approximate limit	Best for
NotebookLM (free)	50 sources per notebook, PDFs up to 200 MB	Multiple sources together, no cost
ChatGPT Free	3 files per day	Short documents, occasional use
Gemini (free or paid)	Up to 1 million tokens (10+ long PDFs)	Very large corpora
Claude Pro ($20/mo)	Up to ~500 pages per PDF	Deep analysis of a single long document
ChatGPT Plus ($20/mo)	80 files every 3 hours	Many documents, frequent use

Quick recommendation:

• First time or want it free: use NotebookLM.
• Single long document (book, 100+ page report): use Claude Pro.
• Cross-referencing 10 or more documents at once: use Gemini.

Confirm current limits on each tool’s official page, as they may change.

Uploading a file is simple in all tools; what makes the difference is the context you give the AI before your first question.

In Claude (claude.ai):

1. Sign in and open a new conversation.
2. Click the clip icon or drag the PDF directly into the chat.
3. Before asking questions, write: “I’m going to ask you questions about this document. It is a [type: contract, report, thesis, manual] about [topic]. Don’t answer anything yet, just confirm you received it.”

In ChatGPT (chatgpt.com):

1. In the text bar, click the clip icon or the + symbol.
2. Upload the PDF or drag the file.
3. Wait for the file name to appear in the chat before sending your first question.

In NotebookLM (notebooklm.google.com):

1. Create a new notebook.
2. In “Add source”, upload the PDF or paste the link.
3. NotebookLM processes the document automatically; you can ask questions from the chat panel.

Tip: if your PDF is a scanned paper document (image), the AI may not be able to read the text. Convert the file to text first with Adobe Acrobat, Smallpdf or another OCR tool.

Most people start with “summarize this document” and get a generic overview. These more specific questions get real results:

To understand the document overall:

• “What are the 5 most important points in this document?”
• “What are the main conclusions the author presents?”
• “What problem does this document solve and what is the proposed solution?”

To find specific information:

• “What does the document say about [specific topic]?”
• “Is there any mention of [name, date, figure] in the text?”
• “In which section is [topic] discussed? Give me the exact quote.”

For deeper analysis:

• “Are there any contradictions or unclear points in the document?”
• “What key information is missing or not well explained?”
• “What are the implications of what’s said on page [number] for [specific situation]?”

For technical or legal documents:

• “Explain the paragraph on page [number] in simple terms.”
• “What technical terms does the document use and what do they mean?”
• “What obligations or rights does this contract give me?”

Always ask the AI to indicate where in the document it found each piece of information. That lets you verify it directly.

When you have several related documents (contract versions, research articles, quarterly reports), AI can cross-reference them and find patterns you’d take hours to detect yourself.

With NotebookLM (the easiest and free way):

1. Create a new notebook.
2. Add all your documents as sources (up to 50 per notebook on the free plan).
3. Ask questions that cross the documents: “What do these three reports agree on and where do they differ?” or “What changed between version 1 and version 2 of the contract?”
4. NotebookLM always tells you which of your sources it found each piece of data in.

With Gemini (for more than 10 documents):

1. At https://gemini.google.com, open a conversation and attach the PDFs.
2. Gemini supports up to 1 million context tokens: enough for dozens of long documents. Confirm the current limit on the official page.
3. Ask: “Analyze all these documents and tell me the common themes and most important discrepancies.”

Key questions for cross-referencing:

• “What are the differences between document A and document B?”
• “What information appears in all the documents?”
• “Which of these documents gives the most complete information on [topic]?”

Want to learn how to organize multiple documents as a knowledge base? Check out How to create your second brain with NotebookLM.

Save these prompts: they work well with any of the tools and any type of document.

To quickly understand a new document:

Read this document and tell me: (1) what it's about in one sentence, (2) the 5 most important points, (3) what action or decision it requires from me, if any.

To find information without knowing which page it’s on:

Does this document mention anything about [specific topic]? If it does, give me the exact quote and tell me where in the document it appears.

To analyze a contract or legal document:

You are an assistant that helps people without legal training understand documents. Read this contract and tell me: (1) what it requires me to do, (2) what it prohibits me from doing, (3) what important risks I should know. Use simple language.

To compare versions of a document:

I have two versions of the same document. Compare them and tell me what changed from the old version to the new one: what was added, what was removed and what was modified.

AI can make mistakes with very technical documents or exact figures. Confirm critical data in the original document. For more text analysis techniques, check out How to use Claude for text analysis.

Problem	Fix
The AI can’t read the PDF	The file may be a scanned image. Convert it to text with Adobe Acrobat or Smallpdf before uploading
The AI says the file is too large	Split the document into smaller parts (by chapter or section) and analyze each part separately
The AI makes up information not in the document	Rephrase asking for exact quotes: “What does the document say exactly about [topic]? Give me the verbatim quote”
I’ve reached the free file limit	Wait until the next day (ChatGPT Free) or use NotebookLM, which has no query limit per file
The response is too general and not useful	Be more specific: instead of “summarize the document”, ask “what does the document say about [specific topic]?”