1. create a group with some one on your contact list. 2. Kick the other person out of group 3. now, attach any file you want to the group and access it via whatsapp web.
Pretty simple to setup and use. for larger files, i would use ftp client on Mobile and use it to transfer files
AFAIK, there is no way to do that in the mobile app, so you will need to use those Whatsapp redirectors, and redirect to your own number.
I made this phone number -> Whatsapp redirector that you can try. Zero server interactions, only JS.
"Whatsapp Dialer" in app store.
Or clicking on this link (replace example phone # with your phone number):
wa.me/17861234567
1 is US's country code. 786 is Miami's / Operator code 1234567 is the phone number