Currently we can only share images in iOS version of the app, contrary to the android version of the app where we have functionality to attach any kind of file.
for android we use: react-native-document-picker
it would be ideal if we could use same modules in both platforms, however the current implementation using react-native-document-picker that works for android gives error for iOS (needs more exploration)

This issue is specifically for a feature where you're in the Zulip app, composing a message, and you touch a button to pull up a screen where you search for a file on your phone, or in iCloud, etc.

For a feature where you have a file open in another app (like a document viewer/editor) and you share the file into Zulip, see #3277.