After plugging in the USB to TTL (3.3V) to the PC with Windows 8.1 in order to connect to the Raspberry Pi according to the lesson in Adafruit Window 8.1 does not seem to have appropriate driver for the device but I manage to get it working using the following steps:
1. Download the driver Profilic_Win8_x64_x86 and extract it 2. Open Device Manager3. Expand Ports (COM & LPT) 4. Right click device name Prolifc USB-to-Serial Comm Port and select Property 5. Select Driver tab 6. Click Update Driver 7. Choose Browse my computer for driver software 8. Choose Let me pick from a list of device drivers on my computer 9. Click Have Disk 10. Choose the folder that you extracted from the downloaded zip file. 11. Choose file "ser2pl.inf" and click Open 12. Click OK 13. After successfully installed restart your PC.