If just the border areas are overlapping you can try using commands at the PDF level.
This will not fix the issue if the images are overlapped.
In the PDF RMB > Edit Text & Image; LMB double click on border (either will work) > RMB > Arrange > Bring to Front (or Back).
It is a limitation in this case. Please refer section 'Plotting Shaded Views' from this documentation link "General usage notes for shaded drafting views".
A workaround (Depending upon your actual requirement) can be to export drawing region as JPG and then print this image as PDF. But there will be considerbale difference in terms of quality, line width etc.