Q: I added some annotations and markups to a PDF. If I then open it with Adobe Reader or PDF Studio the annotations display just fine but when I send the same file to someone else, they say the annotations aren’t displayed. Why is this happening?
A: This is most likely because the individual is using a third party PDF viewer/editor. Not all PDF applications are able to support all of the PDF standard annotations and markups. We see many free PDF applications (such as Preview on the Mac and Okular on Linux) that do not fully support all the annotation and markup features in PDFs.
The publicly available PDF Specifications document (https://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/pdf_reference_1-7.pdf) created by Adobe is 1300 pages long. Most of the free and third part apps that have been created typically only review the minimum standards for the primary features needed by most users which is why they don’t always support all of the features. The developers of these free PDF viewers & editors typically don’t spend the proper amount of time reviewing the PDF specifications to handle all of the features correctly.
Workaround
If you need to ensure that your customers are able to view all of the annotations and markups on the document you can instead “Flatten” the annotations before sending the document to the recipient. Flattening annotations is the act of painting the annotations directly on the page so that the annotations now become content on the page which is supported by nearly all viewers. Once flattened they can no longer be edited.
- Open the PDF document
- You have 3 options available:
- Flatten a Specific Annotation: Using the Hand Tool
or Object Selection Tool 
Select the annotation that you wish to flatten then right-click on the annotation (CTRL + Click on Mac), choose “Flatten” in the context menu. -
Flatten All Annotations:
From the menu, choose Comments > Flatten all Comments
-
Flatten All Annotations on Current Page:
From the menu, choose Comments > Flatten Comments on Current Page
- Flatten a Specific Annotation: Using the Hand Tool
- Save the document to keep the changes
Note: The following annotations (file attachment annotations, links, sounds, and redaction annotations) will NOT be flattened when flattening annotations. Even though technically file attachment annotations, links, sounds, and redaction annotations are annotations, they contain actions that would also be removed if the annotation was flattened and so they remain to not interfere with the functions placed in the PDF.
