The present invention provides a downhole cutting tool for cutting materials at a worksite in a wellbore. The cutting tool includes a cutting end that is adapted to discharge a high pressure fluid therefrom. A power unit in the tool includes a plurality of serially arranged pressure stages, wherein each such stage increases the fluid pressure above its preceding stage until the desired high pressure has been obtained. The high pressure fluid is discharged through the cutting end to effect cutting of a material. A pulsar in the tool is provided to pulse the fluid before it is discharged through the nozzle, which enables the use of lower pressure compared to the pressure required without pulsation of the fluid. A control unit controls the position and orientation of the cutting end relative to the material and may be programmed to cut the material according a predetermined pattern provided to the control unit. An imaging device may be included in the downhole cutting tool to obtain images of the worksite prior to and after the cutting operations.