If you’d like to use for instance Qoppa’s PDF library jPDFProcess.jar in your Maven project, add the following Maven dependency:

<dependency>
    <groupId>com.qoppa.pdfprocess</groupId>
    <artifactId>pdfprocess</artifactId>
    <version>v2017R1.01</version>
    <scope>system</scope>
    <systemPath>${project.basedir}/src/main/resources/jPDFProcess.jar</systemPath>
</dependency>

Make sure to save jPDFProcess.jar under the specified system path, in this case ${project.basedir}/src/main/resources/

You can read more about how to add local jar file to a project in Maven

Note: system dependencies are not copied into resulted jar/war.