PLT TAXIES ONTO RWY ADJACENT TO RAMP AT PUB.

Narrative

WE WERE CLRED APPARENTLY FROM THE RAMP TO RWY 8R BUT 'HEARD' RWY 8L AND BEGAN TO FOLLOW A BIZJET ALSO TAXIING FOR RWY 8L. WE HAD INFORMED GND OF A N VFR DEP AND WERE EXPECTING RWY 8L TO FACILITATE THE TURNOUT. DURING TAXI WE CROSSED FROM THE RAMP TO WHAT APPEARED TO BE A TXWY PARALLELING THE RAMP AND RWYS. WE WERE IMMEDIATELY CONTACTED BY TWR WHO INFORMED US WE WERE ON RWY 8R AND DIRECTING US BACK TO THE RAMP FOR THE REMAINDER OF OUR TAXI. THERE WAS NO APPARENT RWY IDENT SIGNING UNTIL REACHING THE THRESHOLD AREA. THERE WAS NO TFC BESIDES THE BIZJET AND NO SAFETY WAS COMPROMISED ALTHOUGH THE POTENTIAL IS OBVIOUS. FACTORS: HEARING WHAT WAS 'EXPECTED' RATHER THAN WHAT THE TWR APPARENTLY REALLY SAID. MY UNFAMILIARITY WITH THIS ARPT; HAVING ONLY LANDED THERE TWICE IN THE PAST 10 YRS. INADEQUATE SIGNING/DEMARCATION TO SHOW THE N EDGE OF THE RAMP WAS IN FACT A RWY. COPLT WAS FAMILIAR WITH THE ARPT BUT BUSY REVIEWING OUR DEP PROC AND FAILED TO NOTICE OUR POS UNTIL WE WERE CONTACTED BY THE TWR. HE STATED HIS EXPERIENCE WAS THE RWY WAS ONLY USED FOR VFR TOUCH AND GO WHICH CONTRIBUTED (PROBABLY) TO HIS EXPECTATION OF RECEIVING RWY 8L ALSO.