Resize pdf to poster

[user30956902i30d]

I need to resize an 8.5x11 pdf file to a 36x48 file to print for a poster. Can anyone tell me what I need to do?

[Abambo]

That does not work, as the page ratios are different. You can do it, however, you will either have borders or you will have cropped of areas. 

We had a similar issue with posters, that got printed, and I adjusted the background in such a way, that I could scale the file accordingly, without cutting in the usefull area. I did that however with InDesign, and did output the files at the sizes needed.