[PDF-Basics] PDF Font Issue

[Judes]

We are a print house and prints large volume of pdf documents. We experienced a font issue once in a while as the fonts on the pritted page comes out with weired characters. we tried to reproduce the problem by reprinting it. But it was fine when we reprint. Anyone knows why this happens randomly. Could it be something to do with the memory on the pinter.   THanks. Jack