FRA has the SQ BP stock, whereas London does not. You should be able to print at transfer desk in B gates or at the actual gate itself as has already been mentioned.

One thing to consider, as you are flying from London T2 and connecting onwards to SQ on the same day, it might be worthwhile making your way to the SKL F lounge at the T2 satellite building. It is by far the best star facility (for star F ticket pax and TPPS on SQ only).

Do factor in some time to get to your gate for your flight to FRA. That being said, given how poor the star F (non-LH F) offerings are at FRA B gates, nipping into the SKL F at LHR T2 satellite might not be a bad idea.