1) First of all, go ahead and open up your browser and log in to your Gmail account then you need to open the Google Drive.
2) Now all you need to do is upload that PDF or word file to your drive.
3) When it's done double-click on it to open the drive.
4) Now in editor open File > Download as and from the list of available features select the format you want to convert into. If its and pdf file then download it as .docx format, if it's a word file then download as a .pdf format.
Also, there another features you can save the file.