This issue needs to be tested both in Android and iOS (1 device of each, no need to test in multiple devices). In Moodle as admin, configure the following: A page containing an iframe pointing to a PDF file included in the same page. There is one already created in master site > MM Dev Course > Resource: Page > Page with embedded PDF (hosted in same page)  A page containing an iframe pointing to a PDF file in an external site. There is one already created in master site > MM Dev Course > Resource: Page > Page with embedded PDF (external). A page containing an iframe pointing to any website (not a PDF file), and include data-open-external="true" in the iframe. There is one already created in master site > MM Dev Course > Resource: Page > Page with embedded resource displaying embedded PDF. In Site admin > Mobile features > Custom menu items, add an item pointing to an online PDF file. There is one already added in our master site, called "PDF embedded". In the app, open the page in point 1.1. Check that you see a button saying "Open PDF file". Click the button. Check that the PDF file is opened in an external app (Android) or with a viewer on top of the app (iOS). Do the same with the page in point 1.2, the behaviour should be the same. Now open the page in point 1.3. Check that you see a button saying "Open in browser". Click the button. Check that the browser is opened with the page that should have been embedded. Now go to More and open the menu item in point 1.4. Check that you see a button saying "Open PDF file". Click the button. Check that the PDF file is opened in an external app (Android) or with a viewer on top of the app (iOS). Now go offline and check that you can still open the PDFs in points 1.1, 1.2 and 1.4 (the ones where the PDF was embedded directly), but you get an error message if you try to open the iframe in point 1.3. Please notice that PDFs in 1.2 and 1.4 can only be opened in offline if they were previously opened in online, while the PDF in 1.1 can be opened in offline as long as the page has been downloaded (because the file is part of the page, it's not an external file).