Most of the manufactures of polycarbonate sheets advise an approximate fall of 1 in 5.7 i.e. a 10 degree pitch. You will need extra shielding from weathering elements if you take a sheet of less pitch.
Most of these sheets can be cut with the help of a fine tooth saw or garden scissors. The better of the quality of these sheets, the easier it is to cut them. If you want to cut a sheet at a time, you can even use a disk grinder or carborundum. The only disadvantage is that cutting more than one sheet at a time can lead to fusion and welding of sheets.
Before you fix the sheets, drill the holes. The adequate size of the holes is almost 8- 10mm. The holes should be a little larger than the screw’s shaft (at least 2mm) so that there is enough space for the screws to expand and contract. For more details, you can refer to the guide that comes along with the roofing sheets.
You can get appropriate screws from the manufactures of polycarbonate roofing panels. The easiest to use are the one with hexagonal heads. Most sheets are needed to be fixed at every fourth corrugation.