How to attach K-1s for Composite Returns

My partnership files composit returns for all partners in about 10 states where we are non-residents.  We are only provided K-1s for thoses states.  When I added the credit for those states to my California return, the program said that I had to attach copies of the returns, which I assume means the K-1s.  Can I attach those K-1s to an electronically filed return, or do I have to send a paper return?