When saving Illustrator file to pdf, only my 1st layer shows up

[#1]

When I am saving my illustrator file to pdf, only my 1st layer shows up so when merging the layers it shows up. I have tried a lot of different things but not thing worked other than merging the layers. I have hide the only layer, deleted it, changed the settings, and changed the arrangements which none worked. Please help! thank you!

[#2]

When I am saving my illustrator file to pdf, only my 1st layer shows up so when merging the layers it shows up. I have tried a lot of different things but not thing worked other than merging the layers. I have hide the only layer, deleted it, changed the settings, and changed the arrangements which none worked. Please help! thank you!

[#3]

So you create a file, set up a few layers, then save as a PDF and then open the PDF in Illustrator?

Please tell us the version and sstem, where exactly you save the PDF and which options you select for the PDF.