Supplementation of surface-active additives during enzymatic saccharification of biomass helps to increase the activity of cellulase and thus reduces the enzyme dosage in the bioconversion processes. To evaluate the boost effect of additives on enzymatic hydrolysis, five different water-soluble polymers were studied in this work, including poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), polyethylene glycol) (PEG), cationic polyacrylamide (C-PAM), and polyethyleneimine (PEI). Lignin-containing substrates and lignin-free substrates were used in enzymatic hydrolysis tests. It was found that an addition of 10 mg polymer/g-substrate leads to up to a 25.4% increase in glucan hydrolysis and a 13.2% increase in xylan hydrolysis depending on the type of the substrate and polymer. Glucan digestibility achieved from low enzyme loading of 5 FPU/g-glucan with the polymer is comparable to that from 15 FPU/g-glucan enzyme loading. Reducing the amount of the enzyme required could make biomass conversion more cost-effective. Significantly higher yields were obtained with nonionic polymers (PVP, PVA, and PEG) compared with ionic polymers (PEI and C-PAM) for all substrates.