How can I make a poster using PowerPoint
Well, PowerPoint isn't my first choice for printed artwork, and it's not my
second or third either. But, just make the slide size the same dimensions as
the poster, or some even fraction of the final size such as 50%.
Get creative, save often, and print it. Print double size if the page is
half size.
If you plan to send this off for professional printing you might consider
other software, because Ppt doesn't print well to their professional
equipment.
Joh O