diff --git a/Holumbus-Searchengine.cabal b/Holumbus-Searchengine.cabal
--- a/Holumbus-Searchengine.cabal
+++ b/Holumbus-Searchengine.cabal
@@ -1,5 +1,5 @@
 name:          Holumbus-Searchengine
-version:       1.2.1
+version:       1.2.2
 license:       MIT
 license-file:  LICENSE
 author:        Sebastian M. Gauck, Timo B. Huebel, Uwe Schmidt
diff --git a/src/Holumbus/Crawler/PdfToText.hs b/src/Holumbus/Crawler/PdfToText.hs
--- a/src/Holumbus/Crawler/PdfToText.hs
+++ b/src/Holumbus/Crawler/PdfToText.hs
@@ -5,6 +5,7 @@
 module Holumbus.Crawler.PdfToText
 where
 
+import           Control.Concurrent.MVar
 import qualified Control.Exception              as CE
 
 import qualified Data.ByteString.Lazy           as BS
@@ -16,12 +17,13 @@
 import           System.FilePath                ( (</>) )
 import           System.Process                 ( rawSystem )
 import           System.Posix.Process           ( getProcessID )
+import           System.IO.Unsafe               ( unsafePerformIO )
 
 import           Text.XML.HXT.Core
 
 -- ------------------------------------------------------------
 
--- | Converstion of pdf data into plain text. The conversion is done
+-- | Conversion of pdf data into plain text. The conversion is done
 -- by calling an external program @pdftotext@ (contained in linux packages @xpdf@).
 -- IO is done via the ByteString API.
 
@@ -30,22 +32,18 @@
 
 pdfToTextBS     :: BS.ByteString -> IO String
 pdfToTextBS inp = ( do
-                    td      <- getTemporaryDirectory
-                    pid     <- getProcessID
-                    let fn1 = fn td pid "pdfToText.pdf"
-                    let fn2 = fn td pid "pdfToText.txt"
+                    fns@(fn1, fn2) <- requestPdf
                     BS.writeFile fn1 inp
                     _       <- rawSystem "pdftotext" ["-q", "-enc", "UTF-8", fn1, fn2]
                     removeFile fn1
                     res     <- BS.readFile fn2
                     BS.length res `seq`
                       removeFile fn2
+                    releasePdf fns
 
                     return ( fst . utf8ToUnicode . map (toEnum . fromEnum) . BS.unpack $ res )
                   ) `mycatch` ( const $ return "" )
   where
-  fn d p f      = d </> (show p ++ "-" ++ f)
-
   mycatch       :: IO a -> (CE.SomeException -> IO a) -> IO a
   mycatch       = CE.catch
 
@@ -55,5 +53,30 @@
                   arrIO pdfToText
                   >>>
                   perform ( traceString 2 (( "pdfToText result:\n" ++ ) . take 128 . show) )
+
+-- ------------------------------------------------------------
+
+-- The pdftotext call is not thread save
+
+pdfResource    :: MVar (FilePath, FilePath)
+pdfResource
+    = unsafePerformIO $ tmpFiles >>= newMVar
+    where
+      tmpFiles
+          = do td      <- getTemporaryDirectory
+               pid     <- getProcessID
+               let fn1 = fn td pid "pdfToText.pdf"
+               let fn2 = fn td pid "pdfToText.txt"
+               return (fn1, fn2)
+      fn d p f
+          = d </> (show p ++ "-" ++ f)
+
+{-# NOINLINE pdfResource #-}
+
+requestPdf     :: IO (FilePath, FilePath)
+requestPdf     = takeMVar pdfResource
+
+releasePdf     :: (FilePath, FilePath) -> IO ()
+releasePdf     = putMVar pdfResource
 
 -- ------------------------------------------------------------