Aqueous-form additive systems, and methods of blending the same with a matrix resin, are disclosed whereby acrylic-based impact modifier compositions, butadiene-based impact modifier compositions and acrylic-based processing aids are used in aqueous form without the need for isolation to the traditional powder-form. The aqueous additive systems of the present invention provide a means for the design of novel additive compositions. The aqueous additive systems of the present invention also provide a great degree of flexibility in preparation of matrix resin blends and formulations. Additionally, the aqueous additive systems of the present invention allow for the reduced cost of manufacturing additives and reduced cost in blending matrix resin formulations.