dear there is no hard n fast rule for dat it keeps on changing
for example
in 2007 words limit for english essay paper wz 4000-5000 word u can confirm it by seeing sum original paper printed by fpsc
in 2009 it wz 2500-3500 n u can also confirm it by hvin original fpsc's printed question papers n not da ones available in mrkt

so on average 3000-5000 u can select any slab between dez two figures bt frankly quantity hardly matters ive seen pple writing 6 pages n passin essay paper n ive also seen pple writin 30 pages n still unable to score even passin marks