Hi there
It is really easy. Most of the RFID's just transmit data serially which involves only their Tx pin to be connected to the Rx pin of the receiving device, whether it be a microcontroller or a PC. For PC, you will also need an USB to TTL converter. To simultaniously receive data, you can just simply connect RFID's TX to both RX pins (microcontroller's and PC's) at the same time. This is possible because there is only one-way communication happening here i.e RFID transmits and other devices receive.