Preparation of 3d file for printing

I have a 3d file (in obj format) that needs to be resized and prepared for 3d printing in stl format. I have a character model that has been broken down into the following pieces: Head Torso 2 Arms (L & R) 2 Legs (L & R) I have all the files correct and ready for printing, apart from one arm. You will need to resize the right arm so that it matches the left arm perfectly. I need this ASAP.