Hi,
We are about to make Actions available for Flow to allow all kind of documents to be converted, merged, watermarked, secured and OCRed via Flow. Would you like to participate in our beta programme?
Background, the company I work for makes a popular PDF Converter for SharePoint (on premise and Online), which works in SharePoint workflows but is currently being extended to work in Flow as well so it can be used with any system.
What are you looking to do exaclty. Where does the Word document come from (SharePoint, Onedrive, Salesforce, dropbox)? Are you looking to convert other file formats as well?