Also one of my friends suggested me that we have free DFM software’s offered by few PCB manufacturers which is of great help to PCB designers.
Yes they are helpful; yes they are free. But as with everything that is free, there is usually a catch: Most of the time, these programs "lock" you into using that PCB manufacturer's process. You design a board, you can usually only have it fabbed by that company. Furthermore, you learn how to work with that software, and you become "locked" into that software thru learning. If you want to use another board manufacturer, you have to learn their software (if they supply it), or learn another company's software that outputs standard formats.
That standard, from what I understand for PCB manufacturing, is actually the Gerber format. Make sure that whatever tool you are using can output that, and you can use any PCB manufacturer.
Most free software supplied by PCB manufacturers typically is designed and integrated into their process; all the way down to cost and materials. The software typically also has a small learning curve. However, that curve and everything else has the cost that if you want to move to another manufacturer, you may or may not be able to take your design with you (unless the software can export to Gerber).
Then there is EagleCAD - I've heard great things about it; it has its own format (of which you may have seen examples of); most PCB manufacturers can take the Eagle format, in addition to Gerber. I think it will also output Gerber as well. It has a much steeper learning curve than that of the "free" packages; also, while free and low-cost versions of Eagle exist, they are very limited in their functionality; these versions do, however, allow you to make some quite complex designs - you may not need anything else. With that said, though, if you want to go beyond a certain size PCB or number of layers (>2), then be prepared to spend a LOT of cash. EagleCAD is anything but cheap.
Finally, there is the open-source route:
gEDA - I have only played around with the gSchem portion of the project, but what I have seen and heard about the rest is that while the learning curve is super-steep (damn near a vertical wall), you can create just about anything you want with the software (new IC design - no problem). It outputs standard Gerber format, as well as other format files. The project brings together a bunch of tools to allow you to use any PCB manufacturer you want. The software is open-source, and free (although I don't think all - or maybe any - of the software components exist for Windows; this is a set of components mainly geared toward *nix machines), and from what I have been able to gather, fairly robust. No restrictions on PCB size, layers, or anything (other than the really steep learning curve). If you can master gEDA, you can probably use any other tool in the future if needed.