Pages (formerly iWorks Pages) can import and open Microsoft Word documents (.doc, .docx) just fine, so there is nothing more easier than resaving .doc files as .pages file. This of course is only possible if you have access to Apple macOS/OS X/iOS platform.
Without the actual program it will be very hard to reliably produce .pages documents. Some on-line converters claim that they support doc to pages conversion (for example ZAMZAR), but they often save to some previously used format and may not support latest versions.Open DOCX file Open PAGES file
Mobile version of popular word processor from Apple
A word processor and layout tool marketed by Apple