It's in the iOS app only currently. Likely will be in the Desktop PDF reader in the future.

Tested Zotero on iPad today. It's a surprisingly good app.

I mostly use the built-in PDF reader in Zotero for the saved files and I like the implementation where what you highlight is not saved in the PDF (nice if you later want to share the file, but do not want to share your own notes and markups).

But as of now, it's a good but simple PDF reader.

One feature I hope comes to the Windows version is freehand drawing. For me who has the Surface Pro with a pen, it would have been an incredibly handsome feature. On Windows, Drawboard PDF is without a doubt the best program if you use a pen.

It's good to see that what you draw on iPad can be edited on Windows. It gives hope that there are solutions.

There are, of course, other features that would be useful such as being able to create and edit bookmarks, freehand markup for files without text (documents scanned without OCR), inserting hyperlinks, and inserting text fields. All these features are of course not necessary, but nevertheless nice to have.

now, there is draw function in zotero 7 that i had used some time. And we can add text in pdf by zotero 7. This has already met my needs.