If you pad out a piece of writing or a speech with unnecessary words or pieces of information, you include them in it to make it longer and hide the fact that you have not got very much to say.
The reviewer padded out his review with a lengthy biography of the author. [V P n + with]
The generous size of the pictures helped to pad out the story beyond its usefulness. [VERB PARTICLE noun (not pronoun), VERB noun PARTICLE + with]
[Also
VERB noun
PARTICLE]