1. Go to the Settings app on your device and set up your iCloud account first;
To set up iCloud on your iPhone or iPad, please click here to get more information.
2. Open PDF Reader Pro and find Settings on the toolbar, turn on Enable iCloud under FILE VIEWER;
3. The iCloud Drive folder will then be shown on the file list in Documents;
4. Go to Documents, tap at the top right corner and tick the particular file/folder you want to sync with iCloud;
5. Alternatively, you can tap next to the specific file;
6. Tap Move or Copy / Duplicate in the menu;
7. Select iCloud Drive folder from the pop-up menu and tap Move / Paste, then the file will immediately be moved/copied to your iCloud account.