"Information only becomes knowledge in the hands of someone who knows what to do with it."In other words, Information only becomes Knowledge, in the hands of someone who has Knowledge of (knows) what do do with it.
To put it more simply, Information + Knowledge = Knowledge
There's something wrong with this equation!
If knowledge is needed to create knowledge, then where does that knowledge come from? You end up with a "turtles all the way down" argument.
The equation "Information + Knowledge = Knowledge" is like saying A+B=B. This is only true if A=0 (which implies there is no knowledge in information). Maybe that's what Drucker meant?
To find out what Drucker actually meant by this sentences is quite difficult. The article itself doesn't appear online, and is not in the archives of Industry Week. All that seems to remain are references to the sentence above, and to the preceding one "There's no such thing as knowledge management, only knowledgeable people", which also makes little sense, as just because something is a human attribute doesn't make it unmanageable.
My assumption, for what its worth, is that Drucker meant something like this
"Information only becomes actionable in the hands of someone who knows what to do with it."
In other words, knowledge makes information actionable.