Converting from Word to PDF
Open your Word Document
Click File then choose Save As
Browse to where you want to save the document, and then before you save it, change the file type to PDF in File explorer:
Continue to save as usual.
Converting from PDF to Word
Make sure the PDF is saved to your computer.
Navigate to it in File Explorer,
Hover over it and do a right click.
Go to Open With and choose Word.
The Document will then convert to Word, this may take some time depending on the size of the file.