How to summarise a long PDF with AI (free and error-free)
Summarise reports, notes or manuals with ChatGPT, Gemini, Claude or Gemini Notebook: each one’s official limits, the section-by-section method and how to check the summary invents nothing.
Each tool’s official limits (October 2026)
| Tool | What it accepts according to its official page |
|---|---|
| Claude (chat) | PDFs of up to 1,000 pages and 500 MB, up to 20 files per chat. Reads charts and images in PDFs of up to 100 pages. |
| Gemini (app) | Up to 10 files per request, of up to 100 MB. With Google AI Pro or Ultra, a 1-million-token context window (about 1,500 pages). |
| Gemini Notebook (formerly NotebookLM) | Sources of up to 500,000 words or 200 MB, up to 50 sources per notebook on the free version. |
| ChatGPT | Maximum input of roughly 12 pages of text on Free, 40 on Go and Plus, and 250 on Pro (GPT Instant model). |
Limits change often: check the page linked under Sources before relying on them.
The method that works
- Say who the summary is for. Studying is not the same as deciding in a meeting.
- Ask for structure: main idea, key ideas, figures and what remains open.
- Require page references. That way you can check each idea in seconds. Claude recommends referring to pages as your PDF viewer numbers them, not the numbers printed on the document.
- Forbid filling gaps. Add “if it’s not in the document, say so”.
Very long documents: summarise in parts
If the document exceeds the limits or the summary is thin, split it. Google warns that with files that are too large the answer may miss connections or details, and Anthropic recommends splitting long documents into sections. Summarise chapter by chapter, then ask for a summary of the summaries.
How to check it invents nothing
- Pick three ideas at random and find them on the cited page.
- Check every figure: that’s where errors are most common.
- Ask: “Which parts of the document did you not take into account?”
- If you’ll use the summary for something important, read the original. The summary is an aid, not a substitute.
Privacy
Before uploading anything, read what data never to paste. Contracts, payslips, medical reports or work documents with customer data should not be uploaded to a public assistant.
Frequently asked questions
What’s the best free AI for summarising PDFs?
It depends on size. According to the official pages, Claude’s chat accepts PDFs of up to 1,000 pages and Gemini Notebook sources of up to 500,000 words. ChatGPT Free accepts about 12 pages of text per input with GPT Instant. For something short, any will do.
Does AI read the charts and tables in a PDF?
Claude analyses text and visual elements in PDFs of up to 100 pages; above that, text only, according to its help centre. Always check the figures in tables anyway.
Is it safe to upload a work PDF?
Only if your organisation allows it and the document contains no personal data or confidential information. If in doubt, don’t upload it.
Keep reading
Sources
- Upload files to Claude — Anthropic (Claude Help Center)
- Subir y analizar archivos en las aplicaciones de Gemini — Google (Ayuda de Gemini)
- Fuentes admitidas en Gemini Notebook (NotebookLM) — Google
- ChatGPT Pricing (comparativa de planes) — OpenAI
Change log
- : First published with the official limits checked that day.
Educational content, prepared with the help of AI tools, with sources cited. It is not a substitute for professional advice. Tools change fast: if you spot something out of date, write to us at contacto@cognenza.com. How we work.