diff --git a/config/configuration.yml.example b/config/configuration.yml.example
index cdfd516b5..7b19b02bc 100644
--- a/config/configuration.yml.example
+++ b/config/configuration.yml.example
@@ -239,9 +239,28 @@ default:
 
   # Preview for Office documents (Microsoft Office / LibreOffice)
   #
+  # Redmine uses Pandoc to convert supported Microsoft Office and LibreOffice
+  # attachments to Markdown for preview. The settings below named
+  # `markdownized_preview_*` control that Markdown-based preview generation.
+  #
   # Absolute path (e.g. /usr/local/bin/pandoc) to the Pandoc command
   # used to convert supported attachments to Markdown for preview.
   #pandoc_command:
+  #
+  # Timeout when generating Markdown previews using the Pandoc command.
+  # Timeout is set in seconds.
+  # Default: 10
+  #markdownized_preview_generation_timeout: 10
+  #
+  # Maximum source file size in bytes for Markdown preview generation.
+  # Files larger than this limit are skipped.
+  # Default: 10485760 (10 megabytes)
+  #markdownized_preview_max_source_size: 10485760
+  #
+  # Maximum output size in bytes saved after Markdown conversion.
+  # Larger output is truncated to this limit.
+  # Default: 102400 (100 kilobytes)
+  #markdownized_preview_max_output_size: 102400
 
 # specific configuration options for production environment
 # that overrides the default ones
diff --git a/lib/redmine/configuration.rb b/lib/redmine/configuration.rb
index 1c7fdb3a5..1c2426458 100644
--- a/lib/redmine/configuration.rb
+++ b/lib/redmine/configuration.rb
@@ -27,7 +27,10 @@ module Redmine
       'email_delivery' => nil,
       'max_concurrent_ajax_uploads' => 2,
       'common_mark_enable_hardbreaks' => true,
-      'thumbnails_generation_timeout' => 10
+      'thumbnails_generation_timeout' => 10,
+      'markdownized_preview_generation_timeout' => 10,
+      'markdownized_preview_max_source_size' => 10.megabytes,
+      'markdownized_preview_max_output_size' => 100.kilobytes
     }
 
     @config = nil
diff --git a/lib/redmine/markdownizer.rb b/lib/redmine/markdownizer.rb
index 688a2afaf..ac1c67203 100644
--- a/lib/redmine/markdownizer.rb
+++ b/lib/redmine/markdownizer.rb
@@ -27,8 +27,9 @@ module Redmine
     extend Redmine::Utils::Shell
 
     COMMAND = (Redmine::Configuration['pandoc_command'] || 'pandoc').freeze
-    MAX_SOURCE_SIZE = 20.megabytes
-    MAX_PREVIEW_SIZE = 512.kilobytes
+    PREVIEW_GENERATION_TIMEOUT = Redmine::Configuration['markdownized_preview_generation_timeout'].to_i
+    MAX_SOURCE_SIZE = Redmine::Configuration['markdownized_preview_max_source_size'].to_i
+    MAX_OUTPUT_SIZE = Redmine::Configuration['markdownized_preview_max_output_size'].to_i
 
     def self.supports?(filename)
       markdownizable_extensions.include?(File.extname(filename.to_s).downcase)
@@ -50,7 +51,7 @@ module Redmine
       output = Tempfile.new('markdownized-preview')
 
       begin
-        Timeout.timeout(Redmine::Configuration['thumbnails_generation_timeout'].to_i) do
+        Timeout.timeout(PREVIEW_GENERATION_TIMEOUT) do
           pid = Process.spawn(*args, out: output.path)
           _, status = Process.wait2(pid)
           unless status.success?
@@ -72,8 +73,8 @@ module Redmine
         output.close
       end
 
-      preview = File.binread(output.path, MAX_PREVIEW_SIZE + 1) || +""
-      File.binwrite(target, preview.byteslice(0, MAX_PREVIEW_SIZE))
+      preview = File.binread(output.path, MAX_OUTPUT_SIZE + 1) || +""
+      File.binwrite(target, preview.byteslice(0, MAX_OUTPUT_SIZE))
       target
     ensure
       output&.unlink