A method of digitally printing textile substrates includes pretreating a textile substrate with a solution that is configured to limit penetration of aqueous colorant into fibers of the textile substrate, drying the pretreated textile substrate for a predetermined period of time, and digitally printing one or more aqueous colorants onto the dried textile substrate. The pretreatment solution comprises a polyamine with a quaternary ammonium compound attached to the polyamine backbone. The pretreatment solution may be applied onto one or both sides of a textile substrate.