When specifying output dir, copy only the generated pdf

src
  |_ site
    |_ resources
      |_ foo
        |_ bar.pdf

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-pdf-plugin</artifactId>
        <executions>
          <execution>
            <id>pdf</id>
            <phase>site</phase>
            <goals>
              <goal>pdf</goal>
            </goals>
            <configuration>
              <outputDirectory>${project.reporting.outputDirectory}</outputDirectory>
            </configuration>
          </execution>
        </executions>
      </plugin>