Just as an update on this issue. Here is the Mendix support answer (the problem has been solved):
Friday at 17:35, 29-05-2020
“Our R&D team has released a fix this morning that will resolve this issue. In order to access it, you will need to get a new mobile package from Sprintr which will include the update. Phonegap is deprecated as it does not include the latest iOS SDK, so you will need to opt in and build locally.”
It looks like the problem was with InAppBrowser plugin, since it has been changed in config.xml (v4.0.0-dev).
After this change displaying PDF document works as well.
I remember reading somewhere that this is a problem/bug with IOS 13. I'll try to remember where I read this and post a reference here when I find the source.
Not sure if this helps: https://github.com/apache/cordova-plugin-inappbrowser/issues/492
Has anyone created the app with Cordova CLI 5.1.1 (here is removed UIWebView)?
I’ve noticed that in this version is not possible to open (in a browser and in this case in InAppBrowser) PDF Document from the link?
I’ve tested it with CLI 5.0.1 in Xcode 11 and it works as well. The document is correct.