Green’s Dictionary of Slang

pad v.2

[one ‘pads’ or fills the brain with information]

(US black) to inform, to tell.

[US]L. Durst Jives of Dr. Hepcat (1989) 2: Baby you got to elucidate, I don’t know the happenings, all at once, mop! I get the ‘ice berg act.’ So if you just pad my knowledge box I can make everything alreet.

SE in slang uses

In phrases

pad (a bill) (v.)

fraudulently to add items to a bill or to an expense account statement in order to obtain money that one is not actually owed.

[US]Howsley Argot: Dict. of Und. Sl.
[US]M. Braly On the Yard (2002) 244: He threw the requisition over to where Chilly could reach it. ‘How much did you pad it this month?’.