Junk characters occurs when exporting pdf from InDesign CS4.

i have received art files created in illustrator cs5. have placed art files in indesign cs4 , export pdf while open pdf file in acrobat pro 7 junk characters appearing whereas open same pdf file in acrobat pro 9 looks fine. how shown junk characters in acrobat pro 7 only. can let me know why happened in acrobat pro 7 only?

screen shots , settings export you're using.