You could have just converted the existing document to a 2-column layout.
That said, I don't know what you mean by "It produced a single column running down the left side of all the pages". Unless the source you copied from had only short lines terminated by line/paragraph breaks, one would expect the text to span the full width between the margins. There's a macro in the
Cleaning up Text Pasted from Websites, E-mails, PDFs etc. 'Sticky' thread at the top of this forum (
https://www.msofficeforums.com/word/...s-e-mails.html) for cleaning up such text.