Word Copilot Cannot Draft From Attached Reference File: Fix

You attached a PDF, Word document, or text file to your prompt in Microsoft 365 Copilot, but Word shows an error or simply ignores the file when drafting new content. This usually happens because Copilot in Word currently supports file references only in a limited set of scenarios, or because the file format, location, or size violates a hidden constraint. This article explains the exact technical restrictions that cause the failure and gives you a reliable step-by-step workaround to force Copilot to use your reference material.

Why Copilot Ignores an Attached Reference File in Word

Microsoft 365 Copilot in Word does not treat an attached file the same way a human assistant would. The file attachment feature is part of the Compose experience, which is a modal dialog that appears when you click the Copilot icon and select Draft with Copilot. Inside that dialog, a paperclip icon lets you attach up to three files.

The root cause of the failure is one of the following limitations, each of which blocks Copilot from reading the file content:

1. The file is stored locally on your hard drive

Copilot cannot access files that reside only on your local C: drive or any external drive not synced to the cloud. When you attach a local file, Word shows it in the attachment list, but Copilot cannot retrieve the text. The prompt runs against the empty attachment, producing generic output or an error message.

2. The file format is not in the supported list

Copilot in Word supports only .docx, .pdf, .txt, .xlsx, and .pptx as reference files. If you attach a .doc (Word 97-2003), .rtf, .odt, .html, or .csv file, Copilot silently skips it. The attachment appears attached, but the model receives no usable text from it.

3. The file exceeds 3 MB in size

Copilot imposes a per-file size limit of approximately 3 MB. Files larger than this are attached but not processed. The Copilot response will show no evidence that the file was read.

4. The file is not shared with the correct permissions

Even when the file is on OneDrive or SharePoint, Copilot requires that the file be shared with you (the current user) with at least Read access. If the file is stored in a site you cannot access, Copilot cannot read it.

5. You are using the wrong Copilot pane

The file attachment icon appears only in the Draft with Copilot dialog. The side-pane Copilot chat panel (opened via the Copilot button on the Home ribbon) does not support file attachments for drafting. If you paste a file path into the chat pane, Copilot ignores it.

Steps to Force Copilot to Draft From a Reference File

Follow these steps in order. Each step eliminates one of the failure causes listed above.

1. Move the reference file to OneDrive or SharePoint
   Upload the file to your personal OneDrive (Documents folder) or a SharePoint document library you can access. Right-click the file and select Share. Copy the sharing link. Open that link in a browser to confirm you can view the file. If the file is on a shared drive or a local folder, Copilot cannot read it.
2. Convert the file to a supported format
   If the file is .doc, .rtf, .odt, or .html, open it in the appropriate application and save a copy as .docx (Word), .pdf (Save As PDF), or .txt (plain text). For .csv files, open in Excel and save as .xlsx. For .pptx, the format is already supported. Do not use .doc or .rtf as reference files.
3. Check the file size
   In File Explorer, right-click the file and select Properties. Confirm the Size value is under 3 MB. If it is larger, split the content into two files or extract only the relevant section into a new .docx file. Copilot will not read files above the size limit.
4. Open the Draft with Copilot dialog correctly
   In a blank Word document, click the Copilot icon on the Home ribbon. In the Copilot pane that opens on the right, type a prompt such as Draft a proposal based on the attached file. Then click the Compose button at the bottom of the pane. This opens the Draft with Copilot modal dialog. Do not try to attach files directly in the side pane.
5. Attach the file using the paperclip icon
   In the Draft with Copilot dialog, click the paperclip icon (Attach file). Navigate to the file on OneDrive or SharePoint. Select it and click Open. The file name appears in the attachment area. Do not paste a file path or drag and drop a local file.
6. Write a specific prompt that references the attachment
   In the prompt field, write a clear instruction such as Create a three-paragraph executive summary using the information in the attached file. A vague prompt like Draft something may cause Copilot to ignore the attachment. Press Enter or click the Generate button.
7. Verify the output references the file content
   Read the generated draft. If it contains generic placeholder text or repeated phrases not found in your file, Copilot did not read the attachment. Repeat the steps, paying close attention to the file location and format.

If Copilot Still Cannot Read the Attached File

Copilot says the file is not accessible

This error appears when the file is on OneDrive or SharePoint but the sharing link is restricted. Open the file in a browser. If you see a Access Denied or Request Access page, ask the file owner to grant you Read access. After access is granted, wait 30 seconds and repeat the attachment step.

Copilot drafts content that is unrelated to the file

This usually means the file was attached but the prompt did not explicitly ask Copilot to use it. Rewrite the prompt to include the phrase using only the information in the attached file or based on the content of the attached file. Copilot responds better to direct instructions.

Copilot ignores the attachment when drafting from the side pane

The side pane (Copilot chat) does not support file attachments for drafting. You must use the Draft with Copilot dialog. If you prefer the side pane, paste the relevant text from the file directly into the chat prompt instead of attaching the file.

Copilot drafts only the first few paragraphs from a PDF

PDF parsing in Copilot is limited to the first 10 pages or the first 3 MB of text, whichever comes first. If the PDF is a scanned image without selectable text, Copilot cannot extract any content. Convert scanned PDFs to .docx using Word’s Open PDF feature before attaching.

Word Copilot Draft Methods: Attached File vs Embedded Text vs Chat Prompt

Item	Attached File (Draft with Copilot)	Embedded Text in Prompt	Chat Prompt (Side Pane)
Access method	Paperclip icon in Compose dialog	Type or paste content directly	Type query in side pane
File location required	OneDrive or SharePoint	Not applicable	Not applicable
Maximum input size	3 MB per file, up to 3 files	Limited by prompt character count (~8000 chars)	No file attachment support
Supported formats	.docx, .pdf, .txt, .xlsx, .pptx	Plain text only	Plain text only
Best use case	Long external documents	Short excerpts or bullet points	Quick questions without a reference

Use the attached file method when your reference is a complete document longer than a few paragraphs. Use embedded text in the prompt when your reference is a short list or a single paragraph. Use the chat pane only when you do not need an external reference at all.

You can now force Word Copilot to draft content from an attached reference file by moving the file to OneDrive or SharePoint, converting it to a supported format, and using the correct Compose dialog. Next, try the Rewrite with Copilot feature on the generated draft to adjust tone or length. For advanced control, paste the reference text directly into the prompt instead of attaching the file, which bypasses the file-size and format restrictions entirely.