I just use a straight edge and tear the paper. It creates nice edge to it.

I have not confirmed it, so cannot be sure. But Rotarim may not be good for Pt/Pd. There is a contact between metal and metal when it cuts. This can be a cause for black spots. That is another reason why I do not use any metal cutting blades against a metal straight edge.

If it is for some other processes, I would assume it should be fine.

Happy printing,
Tsuyoshi