PDF file change to AI vector format file ?

un-check "convert pages to links to optimize performance" when importing.

In addition to what's already been said, even if the client's PDF contained only vector graphics and text, it's very likely that opening it in Illustrator would present you with the entire layout within a clipping mask, perhaps with many clipping masks inside. That could be why you get this:

just the box only. also, can't edit anything.

By @Kinglouie69

To edit, you would have to release the clipping mask(s), but it may leave you with a confusing mess.

The PDF format does not convert pixel-based image files into vector-based graphics. A PDF is a container for a variety of text and graphics objects. Many people do not understand the differences between vector-based artwork and pixel-based artwork. And they mistakenly assume a file container format such as PDF or EPS will automatically convert a pixel-based image into a clean piece of vector-based artwork.

In my work place we often request vector-based graphics from customers in a variety of formats (AI, EPS, PDF, CDR, AFdesign or SVG). Very often the client will find a copy of his logo saved in a pixel based format such as JPEG or PNG. He might have a vector-based file of it somewhere, but the pixel based image was the first thing he found so he uses that. He launches MS Word or any other document editor and places the JPEG version of that logo into a new document and exports it out as a PDF, expecting it to be all good. Wrong. It doesn't work that way. We see this mistake all the time. Placing a JPEG inside of a PDF does nothing to change the nature of the original JPEG object. It's still a JPEG image wrapped in an additional layer of PDF clothing.

Hi,

So your saying you clicked edit PDF in Acrobat?https://www.printingforless.com/How-to-Edit-PDFs-in-Adobe-Illustrator.html

Thanks Sim

"When we got the client file. They just have PDF format only. In Illustrator CC"

This is often said, though many people don't want to believe it: Illustrator is NOT a general PDF editor. Sometimes it works and that's great, but it can't be relied upon in general.

" change easy to change PDF to Vector. "

How? Do you mean you traced an image? 

"Now. can't to work. just the box only. also, can't edit anything."

Please explain in detail what happens.

Also the version of Illustrator (not "latest" or "up to date")?