Have you selected the apps to sync in iTunes? You don't provide much information to go on. Is this what you are doing?
Connect the iPad to the PC and launch iTunes.
Click on the iPad name on the left side under devices.
Click on the Apps Tab on the right.
Click on all of the aapps in the apps list that you want to sync..
Click on the Sync Apps Heading.
Click on Apply in the lower right corner of iTunes.
If you are doing this and it isn't working, provide some more information as to what is going on.