The rule governs a "pleading, motion, or other paper[.]" The only rational reading of this is that "other paper" means other paper of the category pleadings and motions are, i.e. paper filed with the court. Language later in the rule should clarify that this is, in fact, the case:
"Courts shall presume that pleadings, motions, and other papers are filed in good faith." This is so bog standard and ancient there's Latin for it, ejusdem generis, which states that when a legal document contains general language, like "other papers," following examples, the general language refers to others of the same sort as the listed examples, in this case, documents filed with the court.