If you want to download something from tracker X and upload it to tracker Y you can download it to your seedbox and seed it from there to another tracker, you don't need to download it to you PC. When you download something just save the .torrent file, and upload that torrent file to the other tracker, it saves you time. Only do this if you want to upload the same content, meaning if it's a scene release it is rar-ed, if you want to upload it unrared, you have to unrar it and not every seedbox provider gives you that option, in that case you have to download it to your PC and then upload it you your seedbox and seed it from there.