You can import a PDF into OpenOffice and even edit it, but I don't think it's WYSIWYG. You can convert a text document to PDF with OpenOffice.
I echo Mattu - Adobe Acrobat will do it at a cost. It may be one of those situations where the reader is free but all writers have to be licensed by Adobe (don't quote me on that).
You could Google - here's one link that had some info.