You can transfer your documents by Cloud sync:

1. Please log in your CamScanner account on www.camscanner.com on PC first to check whether your docs on old phone are synced. If not, please pull the doc list on your old phone to sync.

To find your CamScanner login ID:

open the CS app on your old phone-->bottom Me-->Account. 

2. Log in with the same account on your new phone. Your docs will be downloaded after a few minutes.

Please note CamScanner doesn't sync in the background, so please connect your phone with wifi and do NOT close the app otherwise the download may be suspended.
CamScanner syncs only under wifi by default. If you want to sync also with mobile data, please set it in CS app--Me--sync--auto sync--over wifi or mobile network.