Using ChatGPT to analyse documents without losing control

How to get ChatGPT to give you a summary, the tasks or the contradictions in a document without it inventing or deciding for you, and what to remove before uploading.

Text drafted with artificial intelligence. The topic, the angle and the final review are Ibrahin's. How AI is used here

What has happened

ChatGPT now reads PDFs, Word documents, Excel sheets and images, and in seconds gives you back a summary, a task list or a draft email. That has led many people to hand it whole contracts, reports or minutes and go with whatever it returns.

Why it matters to you

Because a well-written summary may have left out exactly what mattered. ChatGPT can skip a figure, misread a sentence or turn a suggestion into a decision. And if two parts of the document contradict each other, it may pick one without telling you.

On top of that, whatever you upload leaves your computer. If the document contains client data, passwords or medical information, the problem starts before you read the answer.

What you can do

1. Remove what isn’t needed before uploading

Full names, addresses, phone numbers, bank details, passwords, medical information or client data: if the task doesn't need them, replace them with labels like [CLIENT], [COMPANY] or [DATE]. Use only the information that's needed.

2. Ask for a summary with a purpose

“Summarise this document” doesn’t say what to keep. Better like this:

Summarise this document in plain language. Explain its purpose, the three main ideas, the decisions made and the pending tasks. Keep doubts and unconfirmed data separate. Don't make anything up.

If the summary is for making a decision, say so: “for someone who has to decide whether to continue the project: what is proposed, what advantages and risks appear and what information is missing”.

3. Pull out the tasks and dates

Extract only the pending tasks. Give the description, owner, deadline, what they depend on and status. If a piece of data doesn't appear, write “not specified”.

Then ask it to order them by priority and flag which can't start until a decision is made. That way you don't do the work in the wrong order.

4. Separate facts, opinions and suggestions

Separate confirmed facts, opinions, suggestions and anything that needs confirming. Don't turn a suggestion into a decision. Flag ambiguous or incomplete sentences and what question would need answering to move on.

5. Ask it to find contradictions, not to resolve them

Look for contradictions within the document. Say which parts clash and why. Don't decide which one is right.

If one page says delivery is on the 10th and another says the 15th, it should warn you, not pick a date on its own.

6. Bear the file type in mind

PDF: if the text can be selected, it reads it better. If it's a scan, check names, figures and tables yourself.
Word: you can ask it to keep the headings and lists or to reorganise the document.
Excel: works best if each column has a clear name and each row is one record. OpenAI recommends descriptive headers and well-organised data.
Images and screenshots: check small text, figures and complex tables by hand.

7. Check the email before you send it

If you ask it to draft a reply, tell it what it mustn't do: “don't accept any terms, don't promise dates and don't make anything up”. And before sending it, check whether it accepts something by accident, promises a date, has a wrong figure or assigns a task to the wrong person.

The recommendation

Use ChatGPT to understand and organise a document, not to decide what it means. Always ask it to separate facts, decisions, tasks and doubts, and check anything with dates, figures, names or commitments against the original. If information is missing, it should say so, not fill it in.

Sources

File Uploads FAQ — OpenAI
Data analysis with ChatGPT — OpenAI
Extracting Insights with ChatGPT Data Analysis — OpenAI

Review

Responsible for publication: Ibrahin. Date: 2026-09-02. Last checked: 2026-09-02.