Hi Huji,
The main job for a PCB designer is to create a physical layout from a schematics provided by an electronic design engineer with much tought given to the electrical functions and contraints of the circuit. You also need to know the mechanical contraints of your physical layout when you design your board. You also need to know possible EMC arising from the different devices on the board and the electrical behaviour of the circuit. With the increasing fast edge electronics devices, you need to know the signal integrity issues and how by placing and routing the board may help to reduce the problems. You need to keep up to date with the pcb fabrication technology and issues since components are becoming smaller and smaller for example BGAs with very fine pitch. Apart from that you may be required to help build footprint library for your company, but normally this is done by someone else if it's a big company. There are few companies in Malaysia that hire PCB Designers like Intel, Motorola, Agilent. They are using all sorts of different softwares like Allegro, BoardStation Mentor Graphics, Protel and etc. Since you are from SHRDC, I think the software that you are using there is Allegro which is a good start because quite a number of companies are using the software here in Malaysia. If u need anymore info, pls PM me. Cheers.