This link suggests it's possible by adding
headers to your pages.
Review the
HP PCL Reference Set to see how you'd embed an image in your header, see the 'start raster graphics' command.
Commands in PCL begin with an ESC character, 0x1b, followed by a few ascii letters defining the command and data. 'Printer reset' for example is as simple as ESC followed by the ascii letter E, and absolutely nothing else.
Remember that PCL is not a document language. It does everything on the level of "move to here, draw this, move to next line, draw that, move there, draw that, next page, draw that"... It will not care or realize if you draw your logo on top of anything else important.