diff --git a/README b/README
index 22540790..8d9b9f05 100644
--- a/README
+++ b/README
@@ -40,9 +40,9 @@ document.
 
 Full installation of GNU Parallel is as simple as:
 
-  wget http://ftpmirror.gnu.org/parallel/parallel-20131022.tar.bz2
-  bzip2 -dc parallel-20131022.tar.bz2 | tar xvf -
-  cd parallel-20131022
+  wget http://ftpmirror.gnu.org/parallel/parallel-20131122.tar.bz2
+  bzip2 -dc parallel-20131122.tar.bz2 | tar xvf -
+  cd parallel-20131122
   ./configure && make && make install
 
 
@@ -51,9 +51,9 @@ Full installation of GNU Parallel is as simple as:
 If you are not root you can add ~/bin to your path and install in
 ~/bin and ~/share:
 
-  wget http://ftpmirror.gnu.org/parallel/parallel-20131022.tar.bz2
-  bzip2 -dc parallel-20131022.tar.bz2 | tar xvf -
-  cd parallel-20131022
+  wget http://ftpmirror.gnu.org/parallel/parallel-20131122.tar.bz2
+  bzip2 -dc parallel-20131122.tar.bz2 | tar xvf -
+  cd parallel-20131122
   ./configure --prefix=$HOME && make && make install
 
 Or if your system lacks 'make' you can simply copy src/parallel
diff --git a/aclocal.m4 b/aclocal.m4
index 5d5340a8..279699f2 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -14,8 +14,8 @@
 
 m4_ifndef([AC_AUTOCONF_VERSION],
   [m4_copy([m4_PACKAGE_VERSION], [AC_AUTOCONF_VERSION])])dnl
-m4_if(m4_defn([AC_AUTOCONF_VERSION]), [2.68],,
-[m4_warning([this file was generated for autoconf 2.68.
+m4_if(m4_defn([AC_AUTOCONF_VERSION]), [2.69],,
+[m4_warning([this file was generated for autoconf 2.69.
 You have another version of autoconf.  It may work, but is not guaranteed to.
 If you have problems, you may need to regenerate the build system entirely.
 To do so, use the procedure documented by the package, typically `autoreconf'.])])
diff --git a/configure b/configure
index ae0910f0..e0f01892 100755
--- a/configure
+++ b/configure
@@ -1,13 +1,11 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.68 for parallel 20131022.
+# Generated by GNU Autoconf 2.69 for parallel 20131122.
 #
 # Report bugs to <bug-parallel@gnu.org>.
 #
 #
-# Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
-# 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software
-# Foundation, Inc.
+# Copyright (C) 1992-1996, 1998-2012 Free Software Foundation, Inc.
 #
 #
 # This configure script is free software; the Free Software Foundation
@@ -136,6 +134,31 @@ export LANGUAGE
 # CDPATH.
 (unset CDPATH) >/dev/null 2>&1 && unset CDPATH
 
+# Use a proper internal environment variable to ensure we don't fall
+  # into an infinite loop, continuously re-executing ourselves.
+  if test x"${_as_can_reexec}" != xno && test "x$CONFIG_SHELL" != x; then
+    _as_can_reexec=no; export _as_can_reexec;
+    # We cannot yet assume a decent shell, so we have to provide a
+# neutralization value for shells without unset; and this also
+# works around shells that cannot unset nonexistent variables.
+# Preserve -v and -x to the replacement shell.
+BASH_ENV=/dev/null
+ENV=/dev/null
+(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
+case $- in # ((((
+  *v*x* | *x*v* ) as_opts=-vx ;;
+  *v* ) as_opts=-v ;;
+  *x* ) as_opts=-x ;;
+  * ) as_opts= ;;
+esac
+exec $CONFIG_SHELL $as_opts "$as_myself" ${1+"$@"}
+# Admittedly, this is quite paranoid, since all the known shells bail
+# out after a failed `exec'.
+$as_echo "$0: could not re-execute with $CONFIG_SHELL" >&2
+as_fn_exit 255
+  fi
+  # We don't want this to propagate to other subprocesses.
+          { _as_can_reexec=; unset _as_can_reexec;}
 if test "x$CONFIG_SHELL" = x; then
   as_bourne_compatible="if test -n \"\${ZSH_VERSION+set}\" && (emulate sh) >/dev/null 2>&1; then :
   emulate sh
@@ -169,7 +192,8 @@ if ( set x; as_fn_ret_success y && test x = \"\$1\" ); then :
 else
   exitcode=1; echo positional parameters were not saved.
 fi
-test x\$exitcode = x0 || exit 1"
+test x\$exitcode = x0 || exit 1
+test -x / || exit 1"
   as_suggested="  as_lineno_1=";as_suggested=$as_suggested$LINENO;as_suggested=$as_suggested" as_lineno_1a=\$LINENO
   as_lineno_2=";as_suggested=$as_suggested$LINENO;as_suggested=$as_suggested" as_lineno_2a=\$LINENO
   eval 'test \"x\$as_lineno_1'\$as_run'\" != \"x\$as_lineno_2'\$as_run'\" &&
@@ -213,21 +237,25 @@ IFS=$as_save_IFS
 
 
       if test "x$CONFIG_SHELL" != x; then :
-  # We cannot yet assume a decent shell, so we have to provide a
-	# neutralization value for shells without unset; and this also
-	# works around shells that cannot unset nonexistent variables.
-	# Preserve -v and -x to the replacement shell.
-	BASH_ENV=/dev/null
-	ENV=/dev/null
-	(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
-	export CONFIG_SHELL
-	case $- in # ((((
-	  *v*x* | *x*v* ) as_opts=-vx ;;
-	  *v* ) as_opts=-v ;;
-	  *x* ) as_opts=-x ;;
-	  * ) as_opts= ;;
-	esac
-	exec "$CONFIG_SHELL" $as_opts "$as_myself" ${1+"$@"}
+  export CONFIG_SHELL
+             # We cannot yet assume a decent shell, so we have to provide a
+# neutralization value for shells without unset; and this also
+# works around shells that cannot unset nonexistent variables.
+# Preserve -v and -x to the replacement shell.
+BASH_ENV=/dev/null
+ENV=/dev/null
+(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
+case $- in # ((((
+  *v*x* | *x*v* ) as_opts=-vx ;;
+  *v* ) as_opts=-v ;;
+  *x* ) as_opts=-x ;;
+  * ) as_opts= ;;
+esac
+exec $CONFIG_SHELL $as_opts "$as_myself" ${1+"$@"}
+# Admittedly, this is quite paranoid, since all the known shells bail
+# out after a failed `exec'.
+$as_echo "$0: could not re-execute with $CONFIG_SHELL" >&2
+exit 255
 fi
 
     if test x$as_have_required = xno; then :
@@ -330,6 +358,14 @@ $as_echo X"$as_dir" |
 
 
 } # as_fn_mkdir_p
+
+# as_fn_executable_p FILE
+# -----------------------
+# Test if FILE is an executable regular file.
+as_fn_executable_p ()
+{
+  test -f "$1" && test -x "$1"
+} # as_fn_executable_p
 # as_fn_append VAR VALUE
 # ----------------------
 # Append the text in VALUE to the end of the definition contained in VAR. Take
@@ -451,6 +487,10 @@ as_cr_alnum=$as_cr_Letters$as_cr_digits
   chmod +x "$as_me.lineno" ||
     { $as_echo "$as_me: error: cannot create $as_me.lineno; rerun with a POSIX shell" >&2; as_fn_exit 1; }
 
+  # If we had to re-execute with $CONFIG_SHELL, we're ensured to have
+  # already done that, so ensure we don't try to do so again and fall
+  # in an infinite loop.  This has already happened in practice.
+  _as_can_reexec=no; export _as_can_reexec
   # Don't try to exec as it changes $[0], causing all sort of problems
   # (the dirname of $[0] is not the place where we might find the
   # original and so on.  Autoconf is especially sensitive to this).
@@ -485,16 +525,16 @@ if (echo >conf$$.file) 2>/dev/null; then
     # ... but there are two gotchas:
     # 1) On MSYS, both `ln -s file dir' and `ln file dir' fail.
     # 2) DJGPP < 2.04 has no symlinks; `ln -s' creates a wrapper executable.
-    # In both cases, we have to default to `cp -p'.
+    # In both cases, we have to default to `cp -pR'.
     ln -s conf$$.file conf$$.dir 2>/dev/null && test ! -f conf$$.exe ||
-      as_ln_s='cp -p'
+      as_ln_s='cp -pR'
   elif ln conf$$.file conf$$ 2>/dev/null; then
     as_ln_s=ln
   else
-    as_ln_s='cp -p'
+    as_ln_s='cp -pR'
   fi
 else
-  as_ln_s='cp -p'
+  as_ln_s='cp -pR'
 fi
 rm -f conf$$ conf$$.exe conf$$.dir/conf$$.file conf$$.file
 rmdir conf$$.dir 2>/dev/null
@@ -506,28 +546,8 @@ else
   as_mkdir_p=false
 fi
 
-if test -x / >/dev/null 2>&1; then
-  as_test_x='test -x'
-else
-  if ls -dL / >/dev/null 2>&1; then
-    as_ls_L_option=L
-  else
-    as_ls_L_option=
-  fi
-  as_test_x='
-    eval sh -c '\''
-      if test -d "$1"; then
-	test -d "$1/.";
-      else
-	case $1 in #(
-	-*)set "./$1";;
-	esac;
-	case `ls -ld'$as_ls_L_option' "$1" 2>/dev/null` in #((
-	???[sx]*):;;*)false;;esac;fi
-    '\'' sh
-  '
-fi
-as_executable_p=$as_test_x
+as_test_x='test -x'
+as_executable_p=as_fn_executable_p
 
 # Sed expression to map a string onto a valid CPP name.
 as_tr_cpp="eval sed 'y%*$as_cr_letters%P$as_cr_LETTERS%;s%[^_$as_cr_alnum]%_%g'"
@@ -559,8 +579,8 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='parallel'
 PACKAGE_TARNAME='parallel'
-PACKAGE_VERSION='20131022'
-PACKAGE_STRING='parallel 20131022'
+PACKAGE_VERSION='20131122'
+PACKAGE_STRING='parallel 20131122'
 PACKAGE_BUGREPORT='bug-parallel@gnu.org'
 PACKAGE_URL=''
 
@@ -1089,8 +1109,6 @@ target=$target_alias
 if test "x$host_alias" != x; then
   if test "x$build_alias" = x; then
     cross_compiling=maybe
-    $as_echo "$as_me: WARNING: if you wanted to set the --build type, don't use --host.
-    If a cross compiler is detected then cross compile mode will be used" >&2
   elif test "x$build_alias" != "x$host_alias"; then
     cross_compiling=yes
   fi
@@ -1176,7 +1194,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures parallel 20131022 to adapt to many kinds of systems.
+\`configure' configures parallel 20131122 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1242,7 +1260,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of parallel 20131022:";;
+     short | recursive ) echo "Configuration of parallel 20131122:";;
    esac
   cat <<\_ACEOF
 
@@ -1309,10 +1327,10 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-parallel configure 20131022
-generated by GNU Autoconf 2.68
+parallel configure 20131122
+generated by GNU Autoconf 2.69
 
-Copyright (C) 2010 Free Software Foundation, Inc.
+Copyright (C) 2012 Free Software Foundation, Inc.
 This configure script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it.
 _ACEOF
@@ -1326,8 +1344,8 @@ cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by parallel $as_me 20131022, which was
-generated by GNU Autoconf 2.68.  Invocation command line was
+It was created by parallel $as_me 20131122, which was
+generated by GNU Autoconf 2.69.  Invocation command line was
 
   $ $0 $@
 
@@ -1742,7 +1760,7 @@ case $as_dir/ in #((
     # by default.
     for ac_prog in ginstall scoinst install; do
       for ac_exec_ext in '' $ac_executable_extensions; do
-	if { test -f "$as_dir/$ac_prog$ac_exec_ext" && $as_test_x "$as_dir/$ac_prog$ac_exec_ext"; }; then
+	if as_fn_executable_p "$as_dir/$ac_prog$ac_exec_ext"; then
 	  if test $ac_prog = install &&
 	    grep dspmsg "$as_dir/$ac_prog$ac_exec_ext" >/dev/null 2>&1; then
 	    # AIX install.  It has an incompatible calling convention.
@@ -1911,7 +1929,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_STRIP="${ac_tool_prefix}strip"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -1951,7 +1969,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_ac_ct_STRIP="strip"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -2002,7 +2020,7 @@ do
   test -z "$as_dir" && as_dir=.
     for ac_prog in mkdir gmkdir; do
 	 for ac_exec_ext in '' $ac_executable_extensions; do
-	   { test -f "$as_dir/$ac_prog$ac_exec_ext" && $as_test_x "$as_dir/$ac_prog$ac_exec_ext"; } || continue
+	   as_fn_executable_p "$as_dir/$ac_prog$ac_exec_ext" || continue
 	   case `"$as_dir/$ac_prog$ac_exec_ext" --version 2>&1` in #(
 	     'mkdir (GNU coreutils) '* | \
 	     'mkdir (coreutils) '* | \
@@ -2055,7 +2073,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_AWK="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -2141,7 +2159,7 @@ fi
 
 # Define the identity of the package.
  PACKAGE='parallel'
- VERSION='20131022'
+ VERSION='20131122'
 
 
 cat >>confdefs.h <<_ACEOF
@@ -2593,16 +2611,16 @@ if (echo >conf$$.file) 2>/dev/null; then
     # ... but there are two gotchas:
     # 1) On MSYS, both `ln -s file dir' and `ln file dir' fail.
     # 2) DJGPP < 2.04 has no symlinks; `ln -s' creates a wrapper executable.
-    # In both cases, we have to default to `cp -p'.
+    # In both cases, we have to default to `cp -pR'.
     ln -s conf$$.file conf$$.dir 2>/dev/null && test ! -f conf$$.exe ||
-      as_ln_s='cp -p'
+      as_ln_s='cp -pR'
   elif ln conf$$.file conf$$ 2>/dev/null; then
     as_ln_s=ln
   else
-    as_ln_s='cp -p'
+    as_ln_s='cp -pR'
   fi
 else
-  as_ln_s='cp -p'
+  as_ln_s='cp -pR'
 fi
 rm -f conf$$ conf$$.exe conf$$.dir/conf$$.file conf$$.file
 rmdir conf$$.dir 2>/dev/null
@@ -2662,28 +2680,16 @@ else
   as_mkdir_p=false
 fi
 
-if test -x / >/dev/null 2>&1; then
-  as_test_x='test -x'
-else
-  if ls -dL / >/dev/null 2>&1; then
-    as_ls_L_option=L
-  else
-    as_ls_L_option=
-  fi
-  as_test_x='
-    eval sh -c '\''
-      if test -d "$1"; then
-	test -d "$1/.";
-      else
-	case $1 in #(
-	-*)set "./$1";;
-	esac;
-	case `ls -ld'$as_ls_L_option' "$1" 2>/dev/null` in #((
-	???[sx]*):;;*)false;;esac;fi
-    '\'' sh
-  '
-fi
-as_executable_p=$as_test_x
+
+# as_fn_executable_p FILE
+# -----------------------
+# Test if FILE is an executable regular file.
+as_fn_executable_p ()
+{
+  test -f "$1" && test -x "$1"
+} # as_fn_executable_p
+as_test_x='test -x'
+as_executable_p=as_fn_executable_p
 
 # Sed expression to map a string onto a valid CPP name.
 as_tr_cpp="eval sed 'y%*$as_cr_letters%P$as_cr_LETTERS%;s%[^_$as_cr_alnum]%_%g'"
@@ -2704,8 +2710,8 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by parallel $as_me 20131022, which was
-generated by GNU Autoconf 2.68.  Invocation command line was
+This file was extended by parallel $as_me 20131122, which was
+generated by GNU Autoconf 2.69.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
   CONFIG_HEADERS  = $CONFIG_HEADERS
@@ -2766,11 +2772,11 @@ _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
-parallel config.status 20131022
-configured by $0, generated by GNU Autoconf 2.68,
+parallel config.status 20131122
+configured by $0, generated by GNU Autoconf 2.69,
   with options \\"\$ac_cs_config\\"
 
-Copyright (C) 2010 Free Software Foundation, Inc.
+Copyright (C) 2012 Free Software Foundation, Inc.
 This config.status script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it."
 
@@ -2861,7 +2867,7 @@ fi
 _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 if \$ac_cs_recheck; then
-  set X '$SHELL' '$0' $ac_configure_args \$ac_configure_extra_args --no-create --no-recursion
+  set X $SHELL '$0' $ac_configure_args \$ac_configure_extra_args --no-create --no-recursion
   shift
   \$as_echo "running CONFIG_SHELL=$SHELL \$*" >&6
   CONFIG_SHELL='$SHELL'
diff --git a/configure.ac b/configure.ac
index 25cb2771..348a851b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,4 +1,4 @@
-AC_INIT([parallel], [20131022], [bug-parallel@gnu.org])
+AC_INIT([parallel], [20131122], [bug-parallel@gnu.org])
 AM_INIT_AUTOMAKE([-Wall -Werror foreign])
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_FILES([
diff --git a/packager/obs/home:tange/parallel/parallel.spec b/packager/obs/home:tange/parallel/parallel.spec
index 4b930b8b..7fbfe496 100644
--- a/packager/obs/home:tange/parallel/parallel.spec
+++ b/packager/obs/home:tange/parallel/parallel.spec
@@ -1,6 +1,6 @@
 Summary:	Shell tool for executing jobs in parallel
 Name: 		parallel
-Version: 	20131022
+Version: 	20131122
 Release: 	1
 License: 	GPL
 Group: 		Productivity/File utilities
diff --git a/src/niceload b/src/niceload
index 0b3bb41f..476f1d90 100755
--- a/src/niceload
+++ b/src/niceload
@@ -24,7 +24,7 @@
 use strict;
 use Getopt::Long;
 $Global::progname="niceload";
-$Global::version = 20131022;
+$Global::version = 20131122;
 Getopt::Long::Configure("bundling","require_order");
 get_options_from_array(\@ARGV) || die_usage();
 if($opt::version) {
diff --git a/src/parallel b/src/parallel
index ebe2b3eb..2e5412cc 100755
--- a/src/parallel
+++ b/src/parallel
@@ -799,7 +799,7 @@ sub get_options_from_array {
 sub parse_options {
     # Returns: N/A
     # Defaults:
-    $Global::version = 20131102;
+    $Global::version = 20131122;
     $Global::progname = 'parallel';
     $Global::infinity = 2**31;
     $Global::debug = 0;
diff --git a/src/parallel.pdf b/src/parallel.pdf
index 21052a9f..5b08908b 100644
Binary files a/src/parallel.pdf and b/src/parallel.pdf differ
diff --git a/src/parallel.texi b/src/parallel.texi
index 8814faf5..3a4a86a0 100644
--- a/src/parallel.texi
+++ b/src/parallel.texi
@@ -1004,10 +1004,10 @@ to determine the number of CPU cores on remote computers).
 @item @strong{--no-notice} (alpha testing)
 @anchor{@strong{--no-notice} (alpha testing)}
 
-Do not display citing notice. A citation notice is printed on stderr
+Do not display citation notice. A citation notice is printed on stderr
 (standard error) only if stderr (standard error) is a terminal, the
-user has not specified @strong{--no-notice} and the user has not run --bibtex
-once.
+user has not specified @strong{--no-notice}, and the user has not run
+@strong{--bibtex} once.
 
 @item @strong{--nice} @emph{niceness}
 @anchor{@strong{--nice} @emph{niceness}}
diff --git a/src/parallel_tutorial.1 b/src/parallel_tutorial.1
index 1a7817d0..73475c46 100644
--- a/src/parallel_tutorial.1
+++ b/src/parallel_tutorial.1
@@ -124,7 +124,7 @@
 .\" ========================================================================
 .\"
 .IX Title "PARALLEL_TUTORIAL 1"
-.TH PARALLEL_TUTORIAL 1 "2013-09-28" "20131022" "parallel"
+.TH PARALLEL_TUTORIAL 1 "2013-09-28" "20131122" "parallel"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
diff --git a/src/sql b/src/sql
index 747aaf64..960ccdca 100755
--- a/src/sql
+++ b/src/sql
@@ -556,7 +556,7 @@ $Global::Initfile && unlink $Global::Initfile;
 exit ($err);
 
 sub parse_options {
-    $Global::version = 20131022;
+    $Global::version = 20131122;
     $Global::progname = 'sql';
 
     # This must be done first as this may exec myself
diff --git a/src/sql.pdf b/src/sql.pdf
index 44ce6288..8482a541 100644
Binary files a/src/sql.pdf and b/src/sql.pdf differ