Hi! My co-workers and I are having a similar problem as other discussions but I haven't seen a solution or reason why yet? There are three of us all working with Illustrator Adobe CC 2015 32 bit (yes - 2015 due to Company decision) one of us is on a Mac and 2 of us are on PC We work on Illustrator files with many layers, and we save them as PDFs (with Preserve Illustrator Editing capabilities and Create Acrobat Layers from Top-Level Layers checked). Instead of working from the native files, we open the PDFs and make the edits and then save as PDF again with same settings as above. (Although the same thing happens when we try to open the ai file) Sometimes one of us will try to open a PDF in Illustrator and get this message: "This file was generated by a newer version of Illustrator. Would you like to import this file? Some data loss will occur" and the file will open with only one flattened layer. We are trying to determine if it is a bit thing (32 bit vs 64 bit), PC vs Mac thing, or CC version issue - that is the question? What is causing this non-compatablity that flattens the layers? Thank you.
... View more