diff --git a/lib/rubrik.rb b/lib/rubrik.rb
index 1f67254..cf4a487 100644
--- a/lib/rubrik.rb
+++ b/lib/rubrik.rb
@@ -3,7 +3,6 @@
 
 require "sorbet-runtime"
 require "pdf-reader"
-require "irb"
 
 module Rubrik
   class Error < StandardError; end
diff --git a/lib/rubrik/document.rb b/lib/rubrik/document.rb
index 270ad08..e8dd5fd 100644
--- a/lib/rubrik/document.rb
+++ b/lib/rubrik/document.rb
@@ -12,19 +12,18 @@ class Document
     SIGNATURE_SIZE = 8_192
 
     sig {returns(T.any(File, Tempfile, StringIO))}
-    attr_reader :io
+    attr_accessor :io
 
     sig {returns(PDF::Reader::ObjectHash)}
-    attr_reader :objects
+    attr_accessor :objects
 
     sig {returns(T::Array[{id: PDF::Reader::Reference, value: T.untyped}])}
-    attr_reader :modified_objects
-
-    sig {returns(PDF::Reader::Reference)}
-    attr_reader :interactive_form_id
+    attr_accessor :modified_objects
 
     sig {returns(Integer)}
-    attr_reader :last_object_id
+    attr_accessor :last_object_id
+
+    private :io=, :objects=, :modified_objects=, :last_object_id=
 
     sig {params(input: T.any(File, Tempfile, StringIO)).void}
     def initialize(input)
@@ -63,7 +62,7 @@ def add_signature_field
           V: signature_value_id,
           Type: :Annot,
           Subtype: :Widget,
-          Rect: [20, 20, 120, 120],
+          Rect: [0, 0, 0, 0],
           F: 4,
           P: first_page_reference
         }
@@ -87,7 +86,7 @@ def interactive_form
     sig {void}
     def fetch_or_create_interactive_form!
       root_ref = objects.trailer[:Root]
-      root = T.let(objects.fetch(root_ref), Hash)
+      root = T.let(objects.fetch(root_ref), T::Hash[Symbol, T.untyped])
 
       if root.key?(:AcroForm)
         form_id = root[:AcroForm]
@@ -111,17 +110,5 @@ def fetch_or_create_interactive_form!
     def assign_new_object_id!
       PDF::Reader::Reference.new(self.last_object_id += 1, 0)
     end
-
-    sig {params(io: T.any(File, Tempfile, StringIO)).returns(T.any(File, Tempfile, StringIO))}
-    attr_writer :io
-
-    sig {params(objects: PDF::Reader::ObjectHash).returns(PDF::Reader::ObjectHash)}
-    attr_writer :objects
-
-    sig {params(modified_objects: T::Array[{id: PDF::Reader::Reference, value: T.untyped}]).returns(T::Array[{id: PDF::Reader::Reference, value: T.untyped}])}
-    attr_writer :modified_objects
-
-    sig {params(last_object_id: Integer).returns(Integer)}
-    attr_writer :last_object_id
   end
 end
diff --git a/lib/rubrik/document/increment.rb b/lib/rubrik/document/increment.rb
index cd79f6c..b9783f3 100644
--- a/lib/rubrik/document/increment.rb
+++ b/lib/rubrik/document/increment.rb
@@ -9,13 +9,15 @@ module Increment
       extend T::Sig
       extend self
 
-      sig {params(document: Rubrik::Document, io: T.any(File, Tempfile, StringIO)).returns(T.any(File, Tempfile, StringIO))}
+      sig {params(document: Rubrik::Document, io: T.any(File, Tempfile, StringIO)).void}
       def call(document, io:)
         document.io.rewind
-        IO.copy_stream(T.unsafe(document.io), T.unsafe(io))
+        IO.copy_stream(document.io, io)
 
         io << "\n"
-        new_xref = Array.new
+
+        new_xref = T.let([], T::Array[T::Hash[Symbol, Integer]])
+        new_xref << {id: 0}
 
         document.modified_objects.each do |object|
           integer_id = T.let(object[:id].to_i, Integer)
@@ -31,18 +33,22 @@ def call(document, io:)
         new_xref_pos = io.pos
 
         new_xref_subsections = new_xref
-          .sort_by { _1[:id] }
-          .chunk_while { _1[:id] + 1 == _2[:id] }
+          .sort_by { |entry| entry.fetch(:id) }
+          .chunk_while {  _1.fetch(:id) + 1 == _2[:id] }
 
         io << "xref\n"
-        io << "0 1\n"
-        io << "0000000000 65535 f\n"
 
         new_xref_subsections.each do |subsection|
-          starting_id = subsection.first[:id]
+          starting_id = T.must(subsection.first).fetch(:id)
           length = subsection.length
 
           io << "#{starting_id} #{length}\n"
+
+          if starting_id.zero?
+            io << "0000000000 65535 f\n"
+            subsection.shift
+          end
+
           subsection.each { |entry| io << "#{format("%010d", entry[:offset])} 00000 n\n" }
         end
 
@@ -51,9 +57,6 @@ def call(document, io:)
         io << "startxref\n"
         io << "#{new_xref_pos.to_s}\n"
         io << "%%EOF\n"
-
-        io.rewind
-        io
       end
 
       private
diff --git a/lib/rubrik/fill_signature.rb b/lib/rubrik/fill_signature.rb
index 61d2814..d739ad5 100644
--- a/lib/rubrik/fill_signature.rb
+++ b/lib/rubrik/fill_signature.rb
@@ -15,7 +15,7 @@ module FillSignature
           private_key: OpenSSL::PKey::RSA,
           public_key: OpenSSL::X509::Certificate,
           certificate_chain: T::Array[OpenSSL::X509::Certificate])
-        .returns(T.any(File, StringIO, Tempfile))}
+        .void}
 
     FIRST_OFFSET = 0
 
@@ -29,8 +29,7 @@ def call(io, signature_value_ref:, private_key:, public_key:, certificate_chain:
       io.gets("<")
 
       first_length = io.pos - 1
-      # we need to double the SIGNATURE_SIZE because the hex encoding double the data size
-      # we also need to sum +2 to account for "<" and ">" of the hex string
+      # We need to sum +2 to account for "<" and ">" of the hex string
       second_offset = first_length + Document::SIGNATURE_SIZE + 2
       second_length = io.size - second_offset
 
diff --git a/lib/rubrik/sign.rb b/lib/rubrik/sign.rb
index 4406837..4a84a63 100644
--- a/lib/rubrik/sign.rb
+++ b/lib/rubrik/sign.rb
@@ -13,6 +13,9 @@ module Sign
            certificate_chain: T::Array[OpenSSL::X509::Certificate])
          .void}
     def self.call(input, output, private_key:, public_key:, certificate_chain: [])
+      input.binmode
+      output.reopen(T.unsafe(output), "wb+") if !output.is_a?(StringIO)
+
       document = Rubrik::Document.new(input)
 
       document.add_signature_field