A file the AI wrote can be rewritten freely — it still has the source. A file you uploaded does not, so the AI works on it in the narrow ways that provably leave the rest of it alone.

Point at the file by putting it on the board or attaching it to your message.

Spreadsheets: writing values in

The AI can write into cells of an .xlsx you uploaded and keep everything else — the formatting, the formulas, the other sheets, the charts.

Cells can be addressed two ways: by reference (B3), or by the row they are in — find the row where Item is Camera, write into the Cost column. The second is usually what you want, because it survives someone inserting a row.

"Fill in the actual costs on this budget from the invoices on the board."

Some cells are refused by name and the rest still applied: a cell holding a formula, the non-anchor half of a merged cell, and anything on a protected sheet. The AI tells you which ones it skipped.

One thing to watch: if the workbook has no formulas at all, any totals in it were pasted values and will not update when the AI writes new numbers around them. It will say so when it hands the file back.

Word files: three safe operations

• Fill placeholders — a template with {{client_name}} style markers gets them filled
• Replace a phrase — an exact match, keeping the formatting it already had
• Append — headings, paragraphs and page breaks added at the end

That is the whole list. It cannot restructure, restyle, reflow, or touch tracked changes. For anything else the AI will say so plainly and offer to author a new file from the content — with the warning that the original's design will not come with it.

PDFs

An uploaded PDF is pages only: reorder, delete, rotate, insert, split, merge. Its words cannot be edited. That has its own article.

Use Cases

• Fill a client's own contract template without rebuilding it
• Write actuals into a budget spreadsheet someone else formatted
• Update a phrase across a document while keeping its styling
• Append a signed-off summary to the end of a report you were sent