What are some risk management techniques for pension funds?

Risk Management is NOT about getting constant (i.e. low volatiliy) returns.
Risk Management is NOT about getting risk with complete certainty.

As Mark Twain said: predicting is difficult, but it is more difficult to predict the future.

Risk Management is about getting rich enough with as much uncertainty as you feel confortable with.

The first step towards risk management for pension funds is knowing the explicit or implied fund's liabilities:
is it a defined benefit fund? then it's quite easy to determine the liabilities.

Is it defined contribution? Then still the fund has, on behalf of the benefitial owners, liabilities to deal with, although they are not explicit and thus are more difficult to be sought after.

You should pursue two different (and at most times contrarian) objectives:
first, maximize the expected surplus of the fund, AFTER the liabilities have been paid.

Second, minimize the VARIANCE of the difference between the liabilities and the assets plus the future contributions to the plan.
That is, you should, on hand
maximize e=(X-B)'E
where X is the Asset Portfolio, B is the portfolio representing the future flows for the fund (i.e. contributions and withdrawals), E is a vector of expected returns for each asset or flow;
and on the other hand
minimize V=VAR{(X-B)'E}
[Note: if X and B are deterministic and E is multinormal, then V= (X-B)'S(X-B) where S ithe covariance matrix for E]

It should be more than obvius that both function are ,generally speaking, not optimal in the same place. Thus, you need a PREFERENCE FUNCTION.
It's usual to have U=e-lV where l is the risk-aversion coefficient.
Depending on how you model your assets and your flows, the function can turn out to be analytically treatable, or you might end up using some kind of simulation

you can look for more information at
AIMR (American Insitute for Market Research)

Obtain the book "How to Make $1,000,000 in the Stock Market Automatically" by Robert Lichello, 3rd Edition, and follow the formula. A way to avoid risk altogether is to put all your money into short term bonds, but I don't like the anemic returns of the latter method.