Hello,
there is no specific law or section which says that documents in original are to be given or as to how many samples are to be given.
However, as a practice the FSL takes the documents in original and take 3-5 samples. The reason being that the pressure points are analyzed by the hand writing expert for which original are required. Also, note that if the original signature are not there then such report filed by the expert can be challenged and also conviction can not be made solely on the basis of the report of the handwritting expert.
regards