Most laserjet printers have a margin of around 2-4mm all around except for the grip side which is slightly bigger. If you can find any settings in the web config set them to their lowest settings or it may be in the driver settings somewhere. I don't know where as I'm not familiar with the HP settings. Other problems maybe the way the document is set up such as the text or table is too close to the edge or the page size is too big and its printed at actual size.
EDIT: Had a look at settings open up Printer Preferences, Advanced, Printer Features turn on the minimise margins.