This can be done by double clicking at the top of your page or clicking on Insert Tab > Header
I suggest typing in a generic header such as 'Document Title'
Date/Time & Page Number
While header is still active, click on the Design tab and select 'Date & Time'
What this will do is replace the date on the document with 'Today's' date and allow you to not have to manually update this field whenever you create a new file.
While still in the Design Tab click on Page Numbers and select a design that you think will work best.
A watermark allows you to insert text or logo on the background of your page in a faint gray preventing other people from stealing your work and branding it as their own.
This is done on the Page Layout tab > Watermark icon.
Note: if you are going to select a picture, then I suggest checking the box to 'washout' so the image is more faint and won't interfere with written text on the document.
Default Font & Size
This step allows you to select the default Font Face, Size, Line Spacing as well as a few other characteristics of your text.
Write a few words on your document, then press CTRL + A to select all text.
Go to the Home tab at top of screen and select 'Paragraph'.
In the video below, I discuss my preferences on the defaults.
Now I don't use this in my default word template for my business, but it is an option that you may find very beneficial.
A cover page will put a nice image or color page to the front of every document you create. This is great for reports or any longer document with multiple pages, such as documentation or manuals.
Saving your Work
The last step is to save your Word Document as a Template so every time you open the file, you can make changes and will be forced to save as a regular doc.x document.
Don't worry, this is a good thing as it will prevent you from accidentally overwriting the settings your template.
Go to File > Save As
Select the 'Save as Type' drop-down and choose 'Word Template (*.dotx)'
My hope is this video and steps listed above help you with your business. I suggest spending a good amount of time on this document and making sure it looks just right for your need. This will help save you time in the long run as you create more materials.
Let me know in the comments below if you have any questions or have your own suggestions on Word Document Template setup.