We need some more information.
What version of ID are you using? and what operating system? Are you exporting to PDF (Print) or PDF (Interactive) if you are offered an option?
PDF export is a background task in ID CS5 and later, so your export may not have completed before you checked. Please activate the checkbox to view the PDF after export so it will open automatically when finished as a way to verify that export is complete.
I've done all those option...well I'm using intel core i5, windows 7. This is the first time it happen, I've tried the other document it worked but only one document I'm using now creating alot of problem
Which version of InDesign? Is it fully patched?
There were some problems with PDF export in CS5 and these were addressed in an update.