I have created a document in Illustrator CS5 and when I go to save as the file as a pdf or eps and open the document in Adobe Reader or Preview there is a thin white line around images and it looks awful. I need this to be fixed before I send the files to my boss. When I save as PDF and select Adobe 4 as the version it appears that the problem is fixed... http://images.creativecow.net/101586/screenshot2012-07-20at10.01.23am.jpg
when you save the PDF... look in the dialog box... try checking the Preserve illustrator editing capability off. basically when this is on, it keeps everything live. stuff like transparency mask and or gradients. This also can drive the file size up.
one other thing you can do is use save for the web jpegs and then bring those into photoshop and re-save as PDFs. this will flatten the image and remove any editing controls. if neither of these options help please let me know and i can help find a workaround.
I have exactly the same problem and I find it is specifically when raster effects like drop shadow or feather are used.
I think its important to not that these lines don't appear on the final printed material. That doesn't help me when I'm exporting for screen...
I tend to print to pdf instead of saving to pdf as this keeps the file size down somewhat. The preserve editing capabilties isn't available in the print dialogue as far as I know. Expoting to jpeg, then re-exporting to pdf from photoshop is simply not a very practical option in my workflow.