Energy harvesting is a technology for extracting a minute amounts of power from ambient sources to typically supply low-power electronic circuits. In this proposed paper a low-cost energy harvester is presented, that uses RF energy sources. An antenna with a voltage doubler is used to convert the low input power to sufficiently high voltage levels for directly driving low-power electronics. While conventional RF energy harvesters are fabricated using conventional fabrication processes, this RF energy harvester is realized by inkjet-printing an antenna and the impedance matching circuit on a photo paper substrate. Only the top layers of such substrates are coated with a polymer, so that they readily absorb the water-based conductive ink. A coplanar waveguide design is presented to fulfill these requirements.