How to preserve document format and structure with Copilot Agent

Hi everyone,

I was building a copilot agent that should be able to accept a document and then make changes to it before returning the new version of that document, which has the same format and structure as the original. What is the best way to accomplish this in copilot studio? So far, I have tried using a power automate flow and external tools but it seems that there is no free included tool that can achieve this task. All the document writing tools seem to be paid services requiring API keys. Is there an alternate free way of achieving this task?

Thank you