No, a text document is simply text, no formatting. It will not keep the original formatting if you go from txt to PDF. It's lost in the conversion to txt.
I really don't think you can import into Word like that. You might (I don't know) get the text and some of the formatting, but it won't preserve it perfectly. You probably need Distiller or something to do that.
What exactly are you trying to do? I mean the broad idea like "fill in a form" or "add a line to a poster".
There are tools for making small changes to PDFs. Jancrow or some other clever designy person will undoubtedly know for sure.