Yes, you can, the shape of distributions are kept. However the normalization change. 
In the case you use scalefact and alpsfact in the run_card, this change of scales can be compensated by using the parameters %$PARP(64)$% and %$PARP(72)$%.
Let's see this in more details:

For ME, the parameters are as follows:
   * scalefact multiplies the (linear) factorization scale and 
      * for non-matched production also the renormalization scale since those are set equal in this case
      * for matched production the renormalization scale of QCD vertices that are not considered "extra jet" vertices
   * alpsfact multiplies the renormalization scale for extra jets for matched production only.

For Pythia, the parameters are:

   * For spacelike showers: PARP(64) is factor of %$K_{T}^{2}$% (note squared, so alpsfact=2 corresponds to PARP(64)=4)
   * For timelike showers: %$\Lambda_{QCD}$% is given in PARP(72), so this value should be multiplied by 0.5 when alpsfact is 2, and by 2 when alpsfact is 0.5. The default value is 0.25 !GeV.

-- Main.SimonDeVisscher - 02 Mar 2009