Some PDF annotation apps store annotations in a way that Notability can't display. If you have a PDF with annotations that don't appear in Notabiilty, you can use these steps to make a new copy of the PDF with annotations that do appear in Notability.
Making a New PDF on iOS
- Open a PDF in the free Adobe Acrobat Reader app.
- Tap the share button (the square with an up arrow at the bottom of the screen).
- Tap "Share File".
- Tap "Share Flattened Copy".
- Tap "Notability".
Making a New PDF on Mac
- Open a PDF in the built-in app named Preview.
- Click "File > Export as PDF..." from Preview's menu bar.
- Navigate to the folder where the new PDF should be saved.
- Click "Save".
- Open the new PDF in Notability.