A family of Microsoft word processing software products for creating web, email, and print documents.
I'm curious - Why not just do the job from Photoshop? Trying to force a word processing program to handle a graphic arts job always will present some degree of challenge.
If you must do it in Word you might try inserting the image into your template using the Watermark tool from the Insert menu or on the Design tab of the Ribbon. Choose the Picture option, select your image, & clear the check for Washout. The image will appear on each page of the document.
Another approach would be to insert the image into the Header of the template. This method amounts to the almost same thing except that the image can be manipulated but the washout effect on screen cannot be removed. The image will print at full intensity, though.
Just keep in mind that printing may be a challenge because word processing programs are not designed for full bleed printing. You probably will need to use the US Letter Borderless [or comparable] option offered by your printer's driver.