diff --git a/README.md b/README.md
index d75d08f..c5b9e4f 100644
--- a/README.md
+++ b/README.md
@@ -34,37 +34,38 @@ License v2* (GPL).
 
 ### Redmine Additionals plugin
 
-  * additionals 2.0.20
+  * additionals 3.0.0
   * https://alphanodes.com/redmine-additionals
   * https://github.com/alphanodes/additionals.git
 
 ### Redmine Checklists plugin (Light version)
 
-  * checklists 3.1.10
+  * checklists 3.1.18
   * https://www.redmine.org/plugins/redmine_checklists
   * https://www.redmineup.com/pages/plugins/checklists
 
 ### Redmine CKEditor plugin
 
-  * ckeditor 1.1.5
+  * ckeditor 1.2.3
   * https://www.redmine.org/plugins/redmine-ckeditor
   * http://github.com/a-ono/redmine_ckeditor
 
 ### Redmine Glossary Plugin
 
-  * glossary 0.9.2
+  * glossary 1.1.0
   * https://www.r-labs.org/projects/rp-glossary/wiki/UsageEn
   * https://github.com/torutk/redmine_glossary
 
 ### Redmine Private Wiki Plugin
 
-  * private_wiki 0.2.0
+  * private_wiki 0.2.0 (mistraloz)
   * http://www.redmine.org/plugins/redmine_private_wiki
-  * https://github.com/BlueXML/redmine_private_wiki
+  * https://github.com/mistraloz/redmine_private_wiki (*fork* con ajustes para
+    Redmine >= 4.0.3)
 
 ### Redmine Q&A plugin
 
-  * questions 1.0.0
+  * questions 1.0.2
   * https://www.redmine.org/plugins/redmine_questions
   * http://www.redminecrm.com/projects/questions
 
diff --git a/config/configuration.yml.example b/config/configuration.yml.example
index a8b6be8..5dbb717 100644
--- a/config/configuration.yml.example
+++ b/config/configuration.yml.example
@@ -179,6 +179,10 @@ default:
   # the ImageMagick's `convert` binary. Used to generate attachment thumbnails.
   #imagemagick_convert_command:
 
+  # Absolute path (e.g. /usr/bin/gs, c:/ghostscript/gs.exe) to
+  # the `gs` binary. Used to generate attachment thumbnails of PDF files.
+  #gs_command:
+
   # Configuration of MiniMagick font.
   #
   # Redmine uses MiniMagick in order to export a gantt chart to a PNG image.
diff --git a/lib/redmine/thumbnail.rb b/lib/redmine/thumbnail.rb
index 79f7843..cc9656b 100644
--- a/lib/redmine/thumbnail.rb
+++ b/lib/redmine/thumbnail.rb
@@ -25,6 +25,7 @@ module Redmine
     extend Redmine::Utils::Shell
 
     CONVERT_BIN = (Redmine::Configuration['imagemagick_convert_command'] || 'convert').freeze
+    GS_BIN = (Redmine::Configuration['gs_command'] || 'gs').freeze
     ALLOWED_TYPES = %w(image/bmp image/gif image/jpeg image/png application/pdf)
 
     # Generates a thumbnail for the source image to target
@@ -79,12 +80,13 @@ module Redmine
         @gs_available = false
       else
         begin
-          `gs -version`
+          `#{shell_quote GS_BIN} -version`
           @gs_available = $?.success?
         rescue
           @gs_available = false
         end
       end
+      logger.warn("gs binary (#{GS_BIN}) not available") unless @gs_available
       @gs_available
     end