Duplicated layers when exporting to PDF

Hello,

I have a quite big Corel File (3 pages, 150 layers across them and thousands of objects). Everything is fine while working with the document but, when I try to export it to PDF, some of the layers appear duplicated. In fact if I export let's say 15 layers, I get around 50 in the PDF file. Some of these layers do not even contain anything but, they make the process of viewing the file with Adobe Reader, very difficult.

I have tried everything, including selecting and deselecting layers (view/print), changing the export settings and so on. 

Does anybody know anyway around this?

Thanks in advance.

Hugo