Valid as of Sep 2017:
EPF, PPF, and a host of other deductions available are all part of 80C, which has an overall limit of 1.5 lac per year. If you have already put in 1.5 lac in PPF, the EPF that is deducted by your employer is giving you no agvantage from tax saving point of view.
If you want to invest additional amount and get tax exemption, there is another way I can suggest. NPS (National Pension Scheme) has an exclusive deduction of 50K a year outside of the 80C 1.5 lac limit. So here's what you can do. Assuming EPF is 50K a year, put only 1 lac in PPF, put the rest 50K in NPS.
Having said this, don't do investments just to save tax. If your financial position allows you to, then put in as much as you can, not just what is necessary to save tax.