Yes, you may do so.
As of version 3.0.0 of WriteMapper, you may now export your WriteMap directly from the app to the PDF format. Simply select the "Export to PDF..." option from the list of export formats within the app, and the PDF will be generated for you on your computer.
For versions of WriteMapper prior to version 3, you'd need to apply the following workaround: First export your WriteMap to DOCX format. Thereafter, opening up the DOCX file in either Microsoft Word or Pages (or your preferred word processing application), export the document to the PDF format.
Do note that if you are facing issues with getting Emojis to export correctly, Pages handles the display of Emojis much better than Microsoft Word does, and it would be preferable to use Pages for exporting to PDF.