I had the same problem. You to do that things :
1- From the PC you want to make the conversion, Add a AcrobatPDFWriter printer, Download the driver of the printer to install it.
2- Open the report, go to File->Print->Printer ( if you have than one printer, choose AcrobatPDFWriter)
3- You have to select print range, copies number.. and then click ok and it's be done
I hope my suggestion help you.