[NTG-pdftex] problem of acrobat reader 4.0 or pdftex?

Hi, while viewing the microtype manual (from texlive2007) using acr4.0 on linux, I found some oddities as shown here: http://www.sendspace.com/file/25thl2 But the problem doesn't occur with acr7.0, xpdf or gv. So it's likely a bug of acr4 on linux? Thanh