ChatGPT, Claude, and Gemini for Reading PDFs: Strengths, Limits, and Comparison

All three tools—ChatGPT GPT-4o, Claude Opus 4/Sonnet 4, and Gemini 2.5 Pro—let you upload PDF files and instantly extract the text, tables, images, and main structure from each document.

Once uploaded, you can ask the AI to summarize, search, extract data, or analyze specific parts of your PDF, saving you the time of reading through it all manually.

ChatGPT GPT-4o is especially effective for PDFs with lots of data, tables, or numbers. It’s designed for users who need summaries, data extraction, and even charts or interactive analysis. It can handle fairly large files, but may slow down or lose some formatting if you upload very long documents.

Claude Opus 4 and Sonnet 4 are best for very long, complex, or technical documents. Thanks to a much larger memory window, they keep track of the entire logical flow and maintain connections between distant sections. Claude is particularly strong at handling PDFs with complicated structures, images, and lengthy text—making it the top choice for manuals, books, and detailed reports.

Gemini 2.5 Pro is the simplest to use for quick overviews, short reports, or if you are already working with Google tools like Drive. It gives fast summaries and suggestions, works well for basic reading and sharing, but can miss some details or precise references in longer or technical files.

All three tools keep the history of your questions in the same session, so you can ask follow-up questions and get deeper analysis without losing your place in the document.

Basic functionalities in PDF reading

ChatGPT GPT-4o allows users to upload PDFs up to 512 MB per file. The system extracts the text and creates an internal representation. It handles files with images, tables, footnotes, complex structures. Summaries, data extraction, section explanations, content analysis, tables, and charts are supported.

Claude Opus 4 and Sonnet 4 read very long PDFs, context window up to 200,000 tokens. Upload via chat or Files API. Extracts text, hierarchical structure, tables, images. Enables deep understanding of technical documents, manuals, contracts.

Gemini 2.5 Pro uploads PDFs via the Gemini interface, Google Drive, or AI Studio. Automatic summary, key point highlighting, action suggestions. Handles large documents (up to 1 million tokens, 2 million coming), with actual limits based on page count and structure.

Technical and practical limits

ChatGPT GPT-4o: context window 128,000 tokens, up to 2 million tokens processed. On very long PDFs (over 900 pages), may slow down, cause formatting errors, incomplete answers. Advanced functions for Plus users.

Claude Opus 4 and Sonnet 4: 30 MB recommended file size for speed and stability. Beyond, risk of time-out increases. Superior analysis of images, complex structures. Extended thinking for multi-step or in-depth analysis.

Gemini 2.5 Pro: large PDF support, some upload errors on very large files or Workspace accounts. Citations often less detailed than Claude or ChatGPT. Service is free for basic features.

Accuracy in understanding and extracting data

Key difference: accuracy in understanding and extracting data from PDFs, especially technical documents.

ChatGPT effective for tables, lists, structured reports, can convert data into other formats (Excel, charts).

Claude: coherence in long documents, connects distant sections, keeps logical flow, ideal for books, policies, technical reports.

Gemini: quick summaries, useful for key points, sometimes oversimplifies, may overlook specific data or numbers.

When you upload a PDF to ChatGPT GPT-4o, Claude Opus 4 (or Sonnet 4), or Gemini 2.5 Pro, the system extracts the content—including text, headings, tables, images, and structural elements—capturing not only the words but also the logical organization like sections and subsections. The AI builds an internal representation or index of the document, storing it in a digital workspace tied to your chat. This allows the model to quickly reference any section when prompted, enabling fast summaries, data extraction, keyword searches, or detailed analysis without re-scanning the file each time.

Each tool loads only the most relevant parts into its active memory (the “context window”—128,000 tokens for ChatGPT, 200,000 for Claude, and up to 1 million for Gemini), dynamically shifting content in and out as needed for large or complex files. All three can extract and reformat tables and data, but Claude maintains logical order and coherence best in long or technical documents, while ChatGPT excels with structured data and interactive outputs, and Gemini focuses on quick summaries and Google integration. If the PDF has unusual layouts or is a scan, Claude generally reconstructs structure better; ChatGPT and Gemini may lose detail or formatting.

For ongoing analysis, the tools keep track of your queries and conversation history within the session, so follow-up questions relate to the same document. Integration features differ: ChatGPT can generate visualizations, Gemini works directly with Google Drive for sharing, and Claude allows persistent file reference across sessions with its API.

Context management and follow-up questions

Maintaining context is fundamental for advanced use.

ChatGPT follows articulated dialogue, supports clarifications, cross-searches.

Claude excels in context management, 200,000-token window, remembers large document parts after many interactions—advantage for manuals, books, contracts.

Gemini is oriented to quick summarization, reduces context detail as conversations grow longer.

Advantages and specific use cases

ChatGPT GPT-4o: analysis of structured data PDFs, tables, financial reports, presentations, combines summaries and visualizations, interactive Q&A, targeted information extraction.

Claude Opus 4 and Sonnet 4: ideal for very long documents—technical books, manuals, policies, contracts, best context retention, coherence, superior handling of images, diagrams, non-standard layouts.

Gemini 2.5 Pro: quick reading, automatic summaries, manuals, business reports, work documents, integration with Google tools, collaboration on Drive.

Updated comparison table

Tool	Maximum PDF size	Context window	Distinctive features	Main limitations
ChatGPT GPT-4o	512 MB / 2M tokens	128,000 active tokens	Structured data, charts, conversation	Slowdown on very long PDFs
Claude Opus 4/Sonnet 4	30 MB recommended	200,000 tokens	Long texts, images, Files API	Time-out above 30 MB, more expensive
Gemini 2.5 Pro	≈1000 pages	1M tokens (2M coming)	Automatic summaries, free, Google integration	Unstable upload, less detailed citations

Considerations for choosing

Best tool depends on PDF type and goal. For professional, extensive, technical documents: Claude (comprehension, context management).

ChatGPT: analysis, data extraction, interactivity.

Gemini: quick reading, Google ecosystem, no extra cost.

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