A lot :)

app/models/pdf_documents/base.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module PdfDocuments
   class Base
     attr_reader :params
@@ -11,7 +13,7 @@ module PdfDocuments
       #                                        exta_bold: 'vendor/assets/fonts/Lexend-ExtraBold.ttf',
       #                                        italic: 'vendor/assets/fonts/Lexend-Regular.ttf'
       #                                      })
-      @prawn_document.font 'Helvetica', size: 12
+      @prawn_document.font "Helvetica", size: 12
       @params = OpenStruct.new(params)
     end
 
@@ -47,7 +49,7 @@ module PdfDocuments
     end
 
     def hr
-      @prawn_document.markup '<hr>'
+      @prawn_document.markup "<hr>"
     end
 
     def markup_options
@@ -63,12 +65,12 @@ module PdfDocuments
     end
 
     def logo
-      @prawn_document.image 'app/assets/images/logo-apfelschule.png', width: 150
+      @prawn_document.image "app/assets/images/logo-apfelschule.png", width: 150
       @prawn_document.move_down 30
     end
 
     def prepare_rich_text(rich_text)
-      { h1: 'h4' }.each do |tag, replacement|
+      { h1: "h4" }.each do |tag, replacement|
         rich_text = rich_text.to_s.gsub("<#{tag}", "<#{replacement}")
         rich_text = rich_text.to_s.gsub("</#{tag}>", "</#{replacement}>")
       end

app/models/pdf_documents/customer_report.rb

@@ -1,19 +1,21 @@
+# frozen_string_literal: true
+
 module PdfDocuments
   class CustomerReport < Base
     private
 
     def generate
       logo
-      @prawn_document.formatted_text_box [{
+      @prawn_document.formatted_text_box [ {
         text: "Dieses Dokument wurd am #{Time.current.strftime('%d %B %Y')} um #{Time.current.strftime('%H:%M:%S')} erstellt.", size: 8, align: :right
-      }], align: :right
+      } ], align: :right
 
       heading1 params.report.name
       rich_text params.report.comment_html
 
       params.report.elements.each.with_index(1) do |element, element_index|
         heading2 "#{element_index} #{element.title}"
-        formatted_text [{ text: element.path, styles: %i[bold italic underline] }]
+        formatted_text [ { text: element.path, styles: %i[bold italic underline] } ]
         move_down(5)
         rich_text element.description_html