I did some quick check.
Here I'm attaching you some results.
I was starting from a MSWord white page generated by MacOS print engine.
Results are:
- the first file is not showed by MacOS Preview and iOS rendering
- the second file is rendered properly in both MacOS and iOS rendering
- the third file (from Radaee) is rendered by MacOS
- the third file (from Radaee) isn't rendered by iOS rendering
We've found many post on Apple official forum about their PDF rendering engine is lacking many annotations' rendering features.
We've also found
forums.adobe.com/docs/DOC-4722.
The way to make Apple PDF rendering engine fully compatible with third part PDF generator is to flatten annotations on the PDF page.
RadaeePDF offer the flat feature as Premium feature.
NOTE: flattening a page you will lose annotations and each image become static on the page itself.