Hey there! Hello!
The exclusive file type for Microsoft Word documents is .docx. You can see the attachment showing all the information you need to know about the example Word document I created. As long as you are using Word, the file type will be the same no matter what type of computer you're on or what it's running, so you don't need to worry about it being different for me on Mac than it might be for you on Windows.
Hope this helped you out! Feel free to ask me any additional questions you may have. :-)
Answer:
classic A4 format, and therefore for 210 x 297 mm sheets
Save the logo as a TEMPLATE.
A template is a pre-developed page layout in soft copy or hard copy used to make pages with the same pattern, style, or design.
In the above scenario, you can prepare a template with you logo in it and save it for future use. In the event that you need to create a new document, you only have to bring up the saved template and edit it with the new information that you need to type.
This way, you will not be hassled to manually add your logo to every new document you create.