Some of the basic PDF viewers might be unable to display advanced annotations - in some cases, you will simply need to protect your annotations and make them stay right there, unchanged, even if someone opens your file. For this purpose, we have an option to save your file as a flattened copy.
Flattening basically makes all the active elements of the file become no longer available for a change. Thus, all the annotations added to the file get so called attached to the PDF and the transparency layer is removed while printing.
Note: As soon as you save the file as flatten, you won't be able to change the annotations, so we recommend having a master copy.