why do faint lines show in acrobat pro 11

Hi kloader,

I think I see what you're referring to. It looks like you created the PDF in Ilustrator CS6, is that correct? It sounds like you may be seeing some screen display artifacts caused by flattening transparency. Since those lines don't change thickness when you zoom in and out, they are most likely a screen display issue only. Please see http://indesignsecrets.com/when-you-see-thin-white-lines-in-your-pdf-files.php. (It's an InDesign article, but the principle is the same.)

Best,

Sara