When you enable iTunes Match all you music must be downloaded from your iTunes Match library in iCloud. If your CDs were matched or uploaded to your iTunes Match library, they will be available to redownload from iCloud after enabling them. You can check to confirm that they were by opening iTunes on your computer, click on Music, go to the View menu at the top, select View Options and check "iCloud Status", then scroll through your songs to confirm that none are marked as ineligible.
After enabling iTunes Match, you can download entire albums, artists or playlists by selecting them in the Music app and tapping the iCloud download icon. Individual songs are downloaded in the background as you play them. Also go to Settings>Music and make sure you have Show All Music set to On (if it's off, you will only see the songs already downloaded to your iPad rather than your entire library).