iBooks does not show up as a Share activities target. It may have something to do with what content type(s) iBooks is registered to handle and what Chrome is advertising.

Hi

There are two different menus in Chrome to share PDF:
- the share button allows you to share the URL of the PDF, if you want to add the link to a post or an email
- the open in button allows you to download the PDF and store it in an external app (like ibooks).

Ibook is the second one.
So to open a PDF in ibook, open the PDF in Chrome, tap on it, tap "open in" in the bottom right corner, and select iBook.

Olivier, is it possible for Chrome to provide multiple activity item sources for PDFs?

I think so, but it requires to download the pdf first.

Gregory, did we recently make Share UI presentation asynchronous? If so, then downloading PDF should not be very hard.

Yes, it is now asynchronous for JavaScript injection. I would imagine though that since downloads can take a much longer amount of time, some UI would be needed to indicate that an operation is occurring. 

Comment #6 has a fair point. I suspect that Safari can simply extract PFD from WKWebView via private API, which is not available for Chrome. We should probably file a bug against WKWebView to allow retrieving the loaded document. Without this API we can't fix the bug.