It doesn't matter how good your printer is, it's not much use if it's at home and you're travelling on business. Step up HP's Officejet 100 Mobile Printer, a compact and highly portable inkjet that's designed to print on A4 paper wherever you are. The squat device has a footprint only slightly larger than a netbook, and it weighs only two and a half kilos including its lithium ion battery, which is included as standard. HP says it provides enough power to print up to 500 pages.As you'd expect from such a compact printer, the diminutive HP has a mostly no-frills specification. There's no duplex, no card reader or fancy colour screen, and no support for wired or wireless networks - instead there's a USB port for connecting to a PC or directly to a camera that supports PictBridge printing. Unusually, Bluetooth is also included as standard, making it possible to print directly from various Bluetooth-enabled smartphones.The Officejet 100 has a sturdy lid that clips down firmly over its top surface, protecting the controls from damage and dust. There's a less sturdy flap to protect the paper output, but frustratingly there's no case included and HP sells only a combined notebook and printer case – we'd prefer a simple slip cover to prevent scratching. We also wish the battery was internal rather than slotting into the back of the printer, where it could be knocked.These gripes aside this feels like a proper printer. As there's room inside for HP's standard ink cartridges colour prints are actually quite cheap. We've been critical of various drivers shipped with HP's inkjet printers, but the version here is simple and effective to use.At the default quality, this printer produced excellent plain paper results, with the bold text and strong, stripe-free colour fills we'd expect from a good home inkjet. A little under 7ppm when printing text is adequately quick, even though this dropped to just over 5.5ppm when repeating the test on battery power.