But you would still require PageMaker for the export. Some alternative presents itself through export to XPS or PDF, which could then be opened in Word.
Only the text will be converted though, special effects from PageMaker might not.
rtf file can be imported to Microsoft Word, or similar word processor and saved in DOC format (or any other actually). However, PageMaker can export its own PMD format to RTF (Rich Text Format), which should be enough for the purposes of transferring the document. Old Adobe PageMaker does not support saving Microsoft Word formats, which makes any kind of pmd to doc conversion somewhat troublesome. Without access to the original PageMaker, it will be pretty complicated to convert pmd to doc and it is unlikely that you will find any pmd to word converter online or any kind of of pagemaker to word converter.