Can I use an extra mattress or padding in the playard for added comfort?

No, you should never add a mattress, pillow, comforter, or padding to the playard. Use only the mattress pad provided by Graco, which measures 27" x 39" (68.5 cm x 99 cm) and is less than one inch thick to meet safety standards. Adding a thicker or different-sized mattress pad can cause a child's head to become trapped between the mattress and the side of the playard, leading to suffocation.