PDF files re sizing for printing

HI

Every time i download a great resource ofr skill, I go to the school printer and it wont downlaod becuase for some reason all the PDF's in my DOcument cloud automatically are in A4 paper size which doesnt work on our school printer, .... only the letter size 8.5 X 11 and I cant not figure out how to convert it. I can do it so easily with my MAC but I only have a Dell right now. PLease help if someone has a suggestion. Thank you so much!

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