I think you can do this. Many compilers allow the programmer to define which pin to used for TX/RX for the UART. You can use this option.
Like wp100 says, the pins are not allocated only for UART and hence can be used independently. But I have read somewhere that using other pins than the ones specified in the manual has some performance issues.
But I haven't seen the performance impact personally though. I think it is just some worst case issue. which you can ignore.