Only if it is itself the manufacturer under the PPWR, for example for a standard unbranded cardboard box, or if you are a micro-enterprise and it is located in the same country as you (Article 3), or simply within the Union under Article 15(12). In other cases, you sign, but your supplier must provide all the necessary information and documentation (Article 16) and cannot refuse to do so.
Read the source article: PPWR EU declaration of conformity: required contents