Adobe Flash Player was discontinued on December 31, 2020, and contents were blocked starting from January 12, 2021. This affected features in Gaaiho PDF Doc and Reader which utilized Flash components (e.g. preview of "packaged" PDF files).
The version 5.4 ensures the compatibility of PDF files after the discontinuance of Flash. Please update to the latest version. Users with Gaaiho PDF 4 or older versions, please considering upgrade to the latest version to ensure optimum user experience.