With WhatsApp we can move documents, photos, videos etc, from Smartphones to computers and vice versa from computer to smartphone.
Or you can make WhatsApp a personal storage for notes or documents, which can be accessed from anywhere using a smartphone or computer without having to enter a password or sign-in first. 
The trick as follows:
We send notes, photos, videos, or other documents to our own. But in WhatsApp we can not send a message to its own number. The trick is that we create a WhatsApp group whose members are just ourselves.
Once the group is created, submit documents, photos, etc. to the group. Obviously because of its members only our own, meaning that can open even our own.
For the computer is by opening WhatsApp Web .
Files, photos, or documents sent to this 'group' can be downloaded or stored on a computer or vice versa on a smartphone, or left in the group. depending on your needs.
How to create a group with members ourselves, just like creating a regular group, only members of it are just our own.
When creating a group in the first step you have to enter participants from the contact list, just enter it as a dummy and then after the group, just remove it again. so its members are just our own.
How to create WhatsApp group, its members only ourselves.
1. Open WhatsApp.
2. Select the menu (vertical three dots).
3. Select New group
4. Enter one participant from the contacts list temporarily
5. Name the group
6. Once the group is finished, open the group,
7. then select menu (vertical three point), select Group info , on participant long press on name to be deleted, then select remove.
