If you want to ensure that your annotations are viewable on iPhone and iPad, you can save a flattened copy of the document. This adds the annotations into the document as regular content that can no longer be edited.
1. Tap the overflow button in the command bar.
2. Select Save A ...
3. Select flattened copy
Saving a reduced file size copy of a file
Saving a password protected copy of a file
Saving a permanently cropped copy of a file