Thanks for your question.
To have all layers in the same PDF image, please perform the following:
1. Go to menu: File | Print to PDF... (or you can use menu: File | Export | PDF Raster... )
2. Make sure to select "One Page for all Layers"
Here's a quick tutorial movie showing me perform those steps (no sound):
Thank you, Simon, for your help.
I figured out why. I selected General - Tile last time which caused the trouble.
I did it last time that printed all the layers in the same image.
But I cannot do it again.
Please see attache files. I need to get the image as 1.pdf showing.