diff --git a/luametalatex-back-pdf.lua b/luametalatex-back-pdf.lua
index c924394..8327273 100644
--- a/luametalatex-back-pdf.lua
+++ b/luametalatex-back-pdf.lua
@@ -5,9 +5,9 @@ local fontdirs = setmetatable({}, {__index=function(t, k)t[k] = pfile:getobj() r
 local usedglyphs = {}
 token.luacmd("shipout", function()
   local voff = node.new'kern'
-  voff.kern = tex.voffset + tex.sp'1in'
+  voff.kern = tex.voffset + pdf.variable.horigin
   voff.next = token.scan_list()
-  voff.next.shift = tex.hoffset + tex.sp'1in'
+  voff.next.shift = tex.hoffset + pdf.variable.vorigin
   local list = node.vpack(voff)
   list.height = tex.pageheight
   list.width = tex.pagewidth
@@ -33,3 +33,14 @@ callback.register("stop_run", function()
   pfile:indirect(pfile.root, string.format([[<</Type/Catalog/Version/1.7/Pages %i 0 R>>]], pfile:writepages()))
   pfile:close()
 end, "Finish PDF file")
+token.luacmd("pdfvariable", function()
+  for n, t in pairs(pdf.variable_tokens) do
+    if token.scan_keyword(n) then
+      token.put_next(t)
+      return
+    end
+  end
+  -- The following error message gobbles the next word as a side effect.
+  -- This is intentional to make error-recovery easier.
+  error(string.format("Unknown PDF variable %s", token.scan_string()))
+end)
diff --git a/luametalatex-baseregisters.tex b/luametalatex-baseregisters.tex
index 98a6e80..f19bd05 100644
--- a/luametalatex-baseregisters.tex
+++ b/luametalatex-baseregisters.tex
@@ -2,6 +2,11 @@
 \catcode`\^^^^ffff=11
 \catcode`\@=11
 \toks0{%
+  do
+  local function frozen(s)
+    local t = token.create(s)
+    return token.new(t.mode, t.command)
+  end
   local dimen_cmd = token.command_id'assign_dimen'
   local tex_params = {}
   local texmeta = getmetatable(tex)
@@ -27,11 +32,35 @@
       return texmetaoldnewindex(t, k, v)
     end
   end
+  local pdf_params = {}
+  pdf.variable_tokens = pdf_params
+  pdf.variable = setmetatable({}, {
+    __index = function(t, k)
+      local v = pdf_params[k]
+      if v then
+        if v.command == dimen_cmd then
+          return tex.dimen[v.index]
+        end
+      else
+        return texmetaoldindex(t, k)
+      end
+    end,
+    __newindex = function(t, k, v)
+      local p = pdf_params[k]
+      if p then
+        if p.command == dimen_cmd then
+          tex.dimen[p.index] = v
+        end
+      else
+        return texmetaoldnewindex(t, k, v)
+      end
+    end,
+  })
 }
 \def\InternalAlloc#1#2#3#4#5{%
   \csname new#3\endcsname#1%
   \global#1=#5\relax
-  \etoksapp0{#2_params["\luaescapestring{#4}"] = token.create"\luaescapestring{\csstring#1}"}
+  \etoksapp0{#2_params["\luaescapestring{#4}"] = frozen"\luaescapestring{\csstring#1}"}
 }
 \def\internalAlloc#1#2#3{%
   \expandafter\InternalAlloc\csname ^^^^fffe#3@#1\endcsname{#1}{#2}{#3}%
@@ -39,11 +68,16 @@
 \def\texAlloc#1#2{%
   \expandafter\InternalAlloc\csname #2\endcsname{tex}{#1}{#2}%
 }
+\def\pdfAlloc{%
+  \internalAlloc{pdf}%
+}
 \texAlloc{dimen}{pageheight}{11in}
 \texAlloc{dimen}{pagewidth}{8.5in}
-% \internalAlloc{tex}{dimen}{pagewidth}
+\pdfAlloc{dimen}{horigin}{1in}
+\pdfAlloc{dimen}{vorigin}{1in}
 \directlua{
-  lua.prepared_code[\csstring#lua.prepared_code+1] = tex.toks[0]
+  lua.prepared_code[\csstring#lua.prepared_code+1] = tex.toks[0] .. "end"
   \the\toks0
+  end
 }
 \endgroup