JPedal contains a module-info.java file, which means it can be used in a modular application with Java 9 or above.
The module name is com.idrsolutions.jpedal.
JPedal also runs on Java 8 and in non-modular applications with no special requirements.
If you are using page flow mode in the JPedal Viewer and running Java 11, this will require 2 OpenJFX modules (javafx.controls and javafx.swing). You will need to:
Go to the OpenJFX site here and download the JavaFX SDK
When running the JPedal jar from the command line, add the 2 required modules to the module path
java --module-path "path/to/javafx-sdk-11/lib" --add-modules=javafx.controls --add-modules=javafx.swing -jar "path/to/jpedal.jar"
Note that page flow works with Java 8 and in non-modular applications with no special requirements.