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Lesson 8 · Intermediate · 15 min

Attaching a Word, PDF or Excel file and asking the right questions

Attach a Word, PDF or Excel file to Copilot Chat and ask the right questions: accepted formats, limits, prompt before and after, exercise and quiz.

By QDNA · Published on · Updated on

Goal
You will be able to attach a document to Copilot Chat, name it in the prompt, restrict the answer to that source and obtain a checkable quotation or an honest "not found".
Skills
Frame
A PDF document, an Excel workbook and a Word file dragged towards the Copilot Chat input box, with the "+" button highlighted.
Illustration generated by AI

Your first attempt, unaided

Attach to Copilot Chat a two-page document you know by heart, then ask it a question whose answer is not in it. Watch whether it tells you so, or answers anyway.

In brief.

Copilot Chat sees none of your documents until you give them to it. You attach a Word, PDF, Excel or PowerPoint file with the "+" button, by drag and drop or with the "/" menu, then you ask a framed question. A good prompt names the file, says what to do with it, restricts Copilot to that source and plans for the case where the information is missing.

  1. 1Attaching is not enough, frame the question

    Without a paid licence, Copilot Chat accesses neither OneDrive, nor SharePoint, nor your email. It reasons only on what you attach. Microsoft lists Word documents, Excel workbooks, PowerPoint presentations and PDFs, and spells out the uses: ask questions about the file, summarise it, run a data analysis. Upload is included, with so-called "standard" access, subject to service capacity at peak times.

    The attached file is stored in your work OneDrive, you can delete it at any time, and it is not used to train the models. Limits on number and size exist, but Microsoft does not put figures on them; the values circulating (three files per day, 512 MB) come from forums and remain uncertain in September 2026.

    Attaching is not enough. The prompt must say what to do with the file. Four habits make the answer reliable. Name the file and its role: "contract_2026.pdf contains the clauses to compare; ignore the appendices". Restrict the source: "rely only on this file". Demand the quotation: "quote word for word the passage used and where it sits". Plan for absence: "if the information is not there, write not found". Without that last instruction, the model fills the gap with a plausible invention.

    Two precautions of form. One targeted file per prompt beats ten mixed documents: research shows that models make poorer use of information placed in the middle of a long context. And an Excel table is prepared before being attached: a single sheet, one header row, one row per record, no total row.

    Diagram "Working with an attached file": Attach the file (Word, Excel, PDF); Ask a precise question; Ask where it is written (page, section); Check in the document. Note: Copilot only reads what you attach: without the file, it invents a generic summaryDiagram "Working with an attached file": Attach the file (Word, Excel, PDF); Ask a precise question; Ask where it is written (page, section); Check in the document. Note: Copilot only reads what you attach: without the file, it invents a generic summary
    Diagram "Working with an attached file"Diagram generated by AI and reviewed

  2. 2Two quotes compared criterion by criterion

    A buyer has received two PDF quotes for renting ten laptops. Both files are attached.

    Weak prompt:

    Compare these two quotes.

    Summarised answer: a paragraph that praises the cheaper quote, mentions a two-year warranty that only one quote specifies, and "estimates" the other supplier's delivery time.

    Strong prompt:

    Compare the two attached quotes, quote_A.pdf and quote_B.pdf, on five criteria: total price excluding VAT, delivery time, payment terms, warranty, equipment take-back. Present a three-column table (criterion, quote A, quote B) and quote the passage from the quote for every cell. If a criterion does not appear in a quote, write "not found" instead of guessing. Rely only on these two files. Finish with three questions to ask the suppliers.

    Summarised answer: a five-row table, two "not found" cells (delivery time for quote B, take-back for quote A), every amount accompanied by its quotation, and three questions targeted at the gaps.

    What changes: the criteria are closed, so comparable. The gaps are visible instead of being filled. Every figure can be checked by opening the quote at the quoted line.

  3. 3Make Copilot answer "not found"

    Write a fictional two-page staff handbook, with no real data, with an article on leave for moving house and nothing on wedding leave. Attach it to Copilot Chat. Here is the starting prompt, to be improved:

    "What does this document say about leave?"

    Add the file name, the restriction to this single source, the demand for a quotation with the article number and the "not found" instruction. Then ask two questions: one about moving house, one about weddings. The second must come back "not found". The composer below guides you on the Sources and Format fields.

    Self-assessment grid: (a) the file is named and the source restricted; (b) the quoted passage exists in your document, at the right article; (c) the trick question did produce "not found".

    Open the prompt composer

  4. 4The messy workbook that doubles the revenue

    A controller attaches a sales workbook as is: three sheets, merged cells, subtotal rows in the middle of the data. Copilot adds the subtotals to the rows, and March revenue comes out almost doubled. The problem lies in the file, not the model. Correction: before attaching, prepare a single sheet, one header row, one row per sale, no total row, typed columns (dates in DD/MM/YYYY format, numeric amounts). Describe this structure in the prompt and ask for the number of rows taken into account and the formula used. Cross-check the result with a manual Excel filter. Rule to remember: a clean file before any calculation prompt.

  5. 5Quiz

    Three questions, instant feedback. Each option comes with an explanation.

    1. You ask "what does this document say about leave?" with the file attached. Which instruction makes the answer checkable?

    2. You compare two PDF quotes. One criterion does not appear in quote B. What should Copilot do according to your prompt?

    3. Without a paid licence, how does Copilot Chat access a file in your OneDrive, according to the perimeter lesson?

  6. 6Proof of mastery

    Paste your final prompt, with the file name and the instruction for missing information, then the answer obtained and the quoted passage as you found it in the document.

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    Criteria

Going further

The lesson on the Copilot Chat perimeter explains why Copilot does not find your files by itself. The term grounding is defined in the glossary. The prompt sheet for executive assistants contains a quote comparison ready to adapt.

Frequently asked questions

Where do the files I attach go?

Microsoft states that they are stored in your work OneDrive, that you can delete them at any time and that they are not used to train the models. They remain subject to your organisation's confidentiality rules.

How many files can I attach, and how big?

Microsoft confirms that limits exist without putting numbers on them. The values circulating on forums (three files per day, 512 MB) are uncertain and may have changed. If a file is refused, reduce the number of files or split the document.

Can I attach a file from my OneDrive without downloading it?

Yes. Type "/" in the input box to open the file menu and pick a document you have access to. It is added to the prompt as if it had been uploaded.

Does Copilot read a scanned PDF?

Text recognition in an image is imperfect. Prefer the digital original or the source Word file. Always check that a requested quotation really exists in the document.

Sources