[GP20]Why it is slow to show a page when showing a PDF file by USB reader?

MS510, MX511, MX750, PB2140, PB9200, PE6800, PB2240, PB7230, PB7210, PB7110, MP780 ST, MP776 ST, MP776, MP777, MP525, MP575, MP526, MP576, 0.3 WALL MOUNT, UNIVERSAL CEILING MOUNT, MW881UST, W1100, MX660P, W1200, W1000, MP626, MP670, MP615P, MP625P, MP525P, W1000+, MX710, 3D GLASSES, 0.6 WALL MOUNT, WIRELESS DONGLE, SP891, MX761, MX810ST, JOYBEE GP1, W600, MP525 ST, SP890, MP782 ST, MP727, MP724, MP735, MP523, MP514, SP920P, SP870, MP722, TEST PJT, MP512, MP512 ST, MP522 ST, SP920, MP522, DATA PROJECTOR LAMP, HOME PROJECTOR LAMP, MP771, W20000, W5000, PE5120, MX501, W700, MS500, W100, CP220, PB8263, PB8253, MP770, MP620, MX812ST, MS612ST, MS614, MX660, MX880UST, MW512, W10000, BENQ LAMP INTRODUCTION, MP515, MP515 ST, MP772 ST, W6000, MP721, MP510, MP721C, CP270, MP623, MP624, MP513, W9000, MP611, PB8230, PB7220, PB7200, MP611C, W500, PB2120, PB8120, PB2220, PB6100, PB6200, SP820, MP723, MP730, CP220C, MP511+, SP830, SP831, MP620C, MP511, MP622, MP622C, MP612, MP612C, PB2250, PB8260, PB6240, PE7700, MP620P, PE8720, MP720P, MP610, CP120, PE7800, PE8700, PB8220, SP840, W600+, MX760, MW811ST, MX613ST, MX615, MX711, MX763, MX764, SH910, MW814ST, W710ST, SH960, W1060, MX850UST, MW851UST, MW516, MX813ST, MS513, MX514, MS500+, 0.4 WALL MOUNT, JOYBEE GP2, GP10, MS512H, SX912, DX818ST, MH740, MW853UST, MX852UST, MW603, MX602, MS524E, MW526E, MX525E