<?php
namespace Witti\FileConverter\Engine\Convert;

use Witti\FileConverter\Engine\EngineBase;
class LibreOffice extends EngineBase {
  protected $cmd_source_safe = FALSE;

  public function getConvertFileShell($source, &$destination) {
    $destination = str_replace('.' . $this->conversion[0], '.'
      . $this->conversion[1], $source);
    return array(
      $this->cmd,
      '--headless',
      '--convert-to',
      $this->conversion[1],
      '--outdir',
      $this->settings['temp_dir'],
      $source
    );
  }

  public function getHelpInstallation($os, $os_version) {
    $help = "";
    switch ($os) {
      case 'Ubuntu':
        $help .= "/usr/bin/libreoffice is symlink to /usr/lib/libreoffice/program/soffice\n";
        $help .= "sudo apt-get install libreoffice\n";
        return $help;
    }

    return parent::getHelpInstallation();
  }

  public function getVersionInfo() {
    $info = array(
      'LibreOffice' => $this->shell($this->cmd . " --version")
    );
    $info["LibreOffice"] = preg_replace('@LibreOffice *@si', '', $info['LibreOffice']);
    return $info;
  }

  public function isAvailable() {
    $this->cmd = $this->shellWhich('libreoffice');
    return isset($this->cmd);
  }

}
<?php
namespace Witti\FileConverter\Engine\Convert;

use Witti\FileConverter\Engine\EngineBase;
class LibreOffice extends EngineBase {
  public function getConvertFileShell($source, &$destination) {
    $destination = str_replace('.' . $this->conversion[0], '.'
      . $this->conversion[1], $source);
    return array(
      $this->cmd,
      '--headless',
      '--convert-to',
      $this->conversion[1],
      '--outdir',
      $this->settings['temp_dir'],
      $source
    );
  }

  public function getHelpInstallation($os, $os_version) {
    switch ($os) {
      case 'Ubuntu':
        return "sudo apt-get install libreoffice";
    }

    return parent::getHelpInstallation();
  }

  public function getVersionInfo() {
    $info = array(
      'LibreOffice' => $this->shell($this->cmd . " --version")
    );
    $info["LibreOffice"] = preg_replace('@LibreOffice *@si', '', $info['LibreOffice']);
    return $info;
  }

  public function isAvailable() {
    $this->cmd = $this->shellWhich('soffice');
    return isset($this->cmd);
  }

}
--- 
+++ 
@@ -3,6 +3,8 @@
 
 use Witti\FileConverter\Engine\EngineBase;
 class LibreOffice extends EngineBase {
+  protected $cmd_source_safe = FALSE;
+
   public function getConvertFileShell($source, &$destination) {
     $destination = str_replace('.' . $this->conversion[0], '.'
       . $this->conversion[1], $source);
@@ -18,9 +20,12 @@
   }
 
   public function getHelpInstallation($os, $os_version) {
+    $help = "";
     switch ($os) {
       case 'Ubuntu':
-        return "sudo apt-get install libreoffice";
+        $help .= "/usr/bin/libreoffice is symlink to /usr/lib/libreoffice/program/soffice\n";
+        $help .= "sudo apt-get install libreoffice\n";
+        return $help;
     }
 
     return parent::getHelpInstallation();
@@ -35,7 +40,7 @@
   }
 
   public function isAvailable() {
-    $this->cmd = $this->shellWhich('soffice');
+    $this->cmd = $this->shellWhich('libreoffice');
     return isset($this->cmd);
   }
 
Use libreoffice rather than soffice to distinguish from OpenOffice.
