Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Became Reoriented
Procedure; Manuals
Descending via the HHOOD3 into PDX; Seattle Center asked us what our airspeed was.  We told them 300 KTS. They asked us to slow to 270 and we complied.  A few minutes later they asked us to slow to 250 and we complied.We then heard them ask another flight if they saw any kind of speed restriction on the HHOOD3 about 280 knots.  They said they didn't see it.  We also re-examined the arrival on our iPad and didn't see it either.  We told ATC that we also didn't see it.  They then wondered if it wasn't yet published on our revisions. ATC further stated that we were the second company flight that day that didn't know about the 280 knot restriction.  ATC then handed us off to PDX approach. We decided to look again and finally saw the note on the right side of the page.  We had been looking in the wrong place (top and bottom).  It said; 'turbojet aircraft descend via Mach number until intercepting 280 KTS; maintain 280 KTS until slowed by the STAR.'  By that time it was too late to call Seattle Center and apologize. Landed without incident; but Captain Young called on the ground to track down Seattle Center's phone number so that we could apologize for our oversight.
A large transport flight crew reported missing a speed restriction note on an arrival page in their iPads. They exceeded the published 280 knots published speed restriction. ATC asked another flight on the frequency if they saw the note and they replied that they did not see the note either. ATC stated that there was another flight that day that did not see the note.