This is because the default setup if this package is for sharing urls to your app.
You need to change/extend/rewrite NSExtensionActivationRule
in Config.plist
of your share extension and stay with react-native-share-extension package. Read more about this key from author and in Apple docs directly.
So you can rewrite entirely rule to apply e.g. pdf files (as said in apple docs):
<key>NSExtensionAttributes</key>
<dict>
<key>NSExtensionActivationRule</key>
<string>
{extensionItems = ({
attachments = ({
registeredTypeIdentifiers = (
"com.adobe.pdf",
"public.file-url"
);
});
})}
</string>
</dict>
All keys for NSExtensionActivationRule
could be found here.