Converting wordprocessor documents to Adobe PDF requires purchased Adobe Acrobat (including Distiller) software (academic pricing is about $50). When you install this, it adds an option to your wordprocessor that lets you "Save as PDF". You would open the Word document and then create a new version of it using "Save as PDF". The version in PDF format must have the filename extension .pdf. The filename.pdf is the file that you would upload on the web.
Once you have created a PDF document, you can submit it (upload it) from the "Confirmation Screen" after you have checked and Saved the AD-416 information.