I just had a look at this, and think I know what the problem is…
Since the pdfs have been uploaded into Moodle, the app uses a reference to the Moodle internal link for this, which is why it doesn;t work in the app, since the link isn’t valid from the app.
There are 2 potential solutions to this (right now, without any tech dev)… and depends on whether users will need to get these pdfs whilst online or offline…
If you need these pdfs to be included in the app download (so available when the user is offline), then best to add a “Resource” activity type in Moodle, and upload the pdf to this. The downside to this approach is that you will need to add a separate “resource” activity for each pdf (rather than including all pdfs in a single page). So you might want a separate section/topic in Moodle for these additional pdfs.
If it’s OK that the user needs to be online to access these, then best to include the full link in the page. So instead of uploading the pdf to Moodle, put the link to the originating site, eg. as you did with the link to the WHO Q&A in this Moodle page activity: https://moodle.communityhealthacademy.org/mod/page/view.php?id=1983
Something to bear in mind here is that sometimes pdfs can get very long/large, and can be tricky to read on small screens (with horizontal and vertical scrolling), so best to keep to pdfs/docs that are a few pages.
Hope that all makes sense, but let me know if you’re still stuck anywhere with this.
Maybe it would be good for use to add a tech dev issue, so that files that are uploaded into pages are also exported so they are available offline for users.