Convert vector graphics to bitmap

[Christian W]

Is there a way in Lyx to automatically convert all eps and pdf vector 
graphics to PNG bitmap format? For printing, my publisher asked me to 
provide a PDF file without vector graphics as this might cause some 
problems. Instead they asked me to convert all vector graphics to PNG format 
with 600 dpi resolution. I am using pdflatex in Lyx to genreate the final 
pdf document.