To completely delete WhatsApp documents and data from iPhone, you can follow these simple steps:
1. Open your WhatsApp application on your iPhone.
2. Tap on "Settings" on the bottom right corner of your screen.
3. Tap on "Storage and Data".
4. Tap on "Manage Storage".
5. You will see a list of all conversations with their respective media sizes. Tap on the conversation that you want to delete the data from.
6. You will see the documents and data that are stored for that conversation, along with their respective sizes.
7. To delete the data, tap on "Edit" on the top right corner of the screen.
8. Tap on the red minus button next to each item you want to delete.
9. Tap on "Delete" to confirm.
10. Repeat the process for all conversations that you wish to delete data from.
11. Once you have deleted all the data you want to delete, you can exit the settings.
Note: This process will delete WhatsApp documents and data from iPhone permanently. Therefore, it is recommended that you proceed with caution and make sure that you only delete the data that you do not need.