Advice please on reading/writing what's app

Is it possible to send pdf and read messages from what’s app ?

Not IOS, Mac or Windows. Preferably Windows.

Do they even publish an api for it ?
From what I can see they dont

No api for whatsapp.
Telegram has an api, it’s the only one i know of.

Well I found this

link text

It’s for iPhone though. Do you think it would be possible to work with it in xojo on Windows?

Short answer no.

Most (all) 3rd Party Apps using the HTML Interface and Web Scraping/Parsing, for “emulating” a WhatsApp Client.

AFAIK there is no web client yet for WhatsApp. It is really very much phone oriented.

But there may be a way for Windows : I see they do have a Windows Phone client, so an UWP app could be conseivable. Now is any technical information ?

It does not look like Whatsapp wishes much third party developments.