Full Bleed Pages in MSWord

Bleed has nothing to do with margins.
For example with a US Letter size page, 8.5” x 11”, a half inch margin would constrain any text or content within a half inch boundary but the page size stays the same.
Without a margin you could allow the text or images right up to the edges of paper.
After printing and guilloteening there is a possibility that the the paper will be trimmed too tightly.
The solution is to extend the four edges of the paper by 1/8th of an inch, this is known as bleed.
So make each page 8.75’ by 11.25””.
If you still want .5”” margins then make each margin 5.125’.

Of course you can leave the paper size as it is and when saving as a PDF specify a 1/8th bleed, that is the normal method.

I hope this helps.

You may find this article helpful although it was designed for InDesign users - indesignskills.com/skills/indesign-bleed