Last updated: October 2026 · Free limits change often and are reported here from third-party comparisons. Check each tool's own plan page before you rely on a number.
Long PDFs are where AI tools earn their keep: a 90-page paper, a contract, lecture slides or a report you need to understand by tonight. Several of the best tools have a free tier, but each one limits it in a different way, so the right choice depends on how long your files are and how many you read. This guide compares the main options and shows how to get a trustworthy summary instead of a confident-sounding wrong one.
- Best free for studying several documents together: Google NotebookLM.
- Best for a quick chat with one PDF: ChatPDF, with a tight daily limit.
- Best on iPhone with a built-in PDF editor: PDFgear.
- Best for very long documents and careful reasoning: Claude (free tier is limited).
- Always: check the summary against the source before you quote or rely on it.
Free limits at a glance
| Tool | Free tier (as reported) | Paid step-up (reported) |
|---|---|---|
| Google NotebookLM | 100 notebooks, 50 sources per notebook, up to 500,000 words or 200 MB per source | Plus reported at $4.99 to $7.99/month depending on source, Pro $19.99/month |
| ChatPDF | 2 PDFs a day, 120 pages and 10 MB per PDF, 50 questions a day | Plus about $5/month |
| PDFgear | Free PDF app with an AI Copilot; limits not published in the guide I read | Check the app |
| ChatGPT | Free, limited uploads and usage | Plus $20/month |
| Claude | Free, limited usage | Pro $20/month (about $17 billed annually) |
Google NotebookLM: best free option for studying
NotebookLM is built for working with your own documents. You add sources (PDFs, notes, links) to a notebook, then ask questions, and answers are tied to the specific source passages, which makes them easier to check. A 2026 comparison reports that the free plan allows 100 notebooks and 50 sources per notebook, with each source up to 500,000 words or 200 MB, and that Audio and Video Overviews are included but share a usage budget with chat. That budget reportedly refreshes every five hours up to a weekly cap. It's a third-party report, so confirm the current limits with Google.
Choose it if you are studying from several documents, like a course pack, and want citations to check.
ChatPDF: fastest for one file, but tightly capped
ChatPDF is a simple "upload a PDF and ask questions" tool that works in a phone browser. One pricing page lists the free plan at two PDFs a day, up to 120 pages and 10 MB each, and 50 questions a day. The old version of this article said "several uploads" and a "good number of questions," which was too vague. If you read more than two files a day, you'll hit the wall quickly.
Choose it if you want a quick answer from one PDF without setting anything up.
PDFgear: a PDF app with a Copilot
PDFgear is a PDF reader and editor with an AI assistant, and it has an iPhone app. According to its iOS guide, you open a PDF in the Files tab, tap the Copilot icon, choose Chat Now, and ask for a summary or ask follow-up questions in the same chat. You can export the chat as text. The guide doesn't list free-tier limits, and the old article's "completely free of charge" claim wasn't backed by a source, so check the app's current terms.
Choose it if you want one app to read, mark up and summarize PDFs on your iPhone.
ChatGPT, Claude and Gemini: general chatbots with file upload
The old version said free ChatGPT and Gemini don't accept PDF uploads and you have to paste text. That's out of date: a 2026 comparison lists ChatGPT and Claude as both having free tiers with limited uploads. Limits vary by account and change often, and Google's free Gemini plan has its own caps on files and usage, so check the app. A few notes:
- Claude is often recommended for very long PDFs and careful reasoning. See How to Use Claude AI on iPhone.
- ChatGPT is a good all-rounder, especially when you want to compare more than one document.
- Gemini works well if your files already live in Google Drive. For the Android angle, see Best Free AI Apps for Android.
How to get a summary you can trust
- Ask for structure. Try: "Summarize this PDF in 5 bullet points, then list the 3 key terms, then the main conclusion."
- Ask for page references. "Cite the page number for each point." Then spot-check two or three of them.
- Split long files. If a tool has a page cap, upload it in chapters and combine the summaries.
- Check numbers and names yourself. Tools can misread tables or state things the document doesn't say.
- Ask what's missing. "What does this document not cover?" often reveals gaps.
- Read the key section yourself. Use the summary to navigate, not to replace reading what you'll be graded or held accountable for.
Copy-and-use prompt template
Paste this after you upload a document, and change the brackets:
"You are helping me study [subject]. Summarize this document in under 200 words for a beginner. Then list 5 key terms with one-line definitions, and 3 questions I could be asked about it. Cite the page for each point. If something isn't in the document, say so instead of guessing."
Privacy: what happens to your PDF
- Uploading a PDF sends its contents to a third party. Read each tool's data and training policy, and look for an opt-out from training.
- Don't upload confidential contracts, medical records, student records, ID documents or anything under a non-disclosure agreement to a free tool.
- If you need privacy, remove names and numbers first or use a tool your school or employer has approved.
Follow your school's rules
Many schools allow AI for understanding material but not for writing graded work. Check your course policy before you submit anything AI-assisted, and cite the tool if your institution asks you to.
FAQ
Is there a truly free AI PDF summarizer?
NotebookLM has the most generous free plan among the reported options, but every free tier has limits, so read them before you rely on one.
Can I do this on an iPhone?
Yes. ChatPDF works in a mobile browser, PDFgear has an iOS app with a Copilot, and the major chatbots have apps.
Are AI summaries accurate?
Often, but not always. Citations help you check, and answers without a source should be treated as a starting point.
Which is best for a textbook?
NotebookLM (source limits are large) or Claude (long-document focus). Split by chapter if a tool has a page cap.
Is it cheating?
It depends on your school's rules. Using AI to understand a reading is usually different from using it to write an assignment, but check your policy.
My pick
Start with NotebookLM for study sessions, keep ChatPDF for a one-off file, and use Claude or ChatGPT when you need a deeper explanation. Check every summary against the original before you rely on it. For more everyday iPhone tips, see 10 iPhone Settings You Should Change Right Now.
Sources: Elephas: NotebookLM free plan limits (third-party) · AI Tools Atlas: ChatPDF pricing (third-party) · PDFgear: Chat with PDF on iOS · AI Toolkit Pro: best AI PDF tools 2026