Rosin, as a traditional internal sizing agent, has not been extensively used under neutral or alkaline pH due to the ineffectiveness of aluminum sulfate (alum) under such conditions. Rosin has some inherent advantages relative to the cellulose-reactive agents alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA). Rosin is generally not subject to problems with paper-surface slipperiness, sizing reversion, or hydrolysis. Rosin products are widely used on account of their favorable price, but they are pH-sensitive, and their emulsions can become unstable and lose homogeneity during storage. Developing a rosin-sizing system from domestic sources is a primary objective of this study. Crude rosin was obtained from mixed pine stumps by hexane extraction. Fortification was carried out with maleic acid anhydride to alter the structure of the rosin. The material was then saponified until reaching an acid number of 26. Part of the rosin was premixed with alum, using a blender. To make the alum-premixed sizing formulation positively charged, a high-charged cationic polymer (poly-DADMAC) was added. Each sizing agent formulation was tested with three pulp types. Charge demand values of bleached chemical pulp, unbleached kraft pulp and recycled pulp were determined, and the sizing behavior of the resulting paper was compared. For comparison, paper was also sized conventionally with alum and rosin. Greater sizing performance was obtained with the premixed rosin formation than with the conventional sizing. Moreover, it was observed that the yellowish coloration of the paper was decreased with increasing pre-mixed rosin sizing agent usage in the case of the bleached furnish.