Based on Debian patch, see http://patch-tracker.debian.org/patch/series/view/pdftk/1.45-1/customise_build_parameters

diff -ruN pdftk-1.45-dist.orig/pdftk/Makefile.Base pdftk-1.45-dist/pdftk/Makefile.Base
--- pdftk-1.45-dist.orig/pdftk/Makefile.Base	2012-12-06 19:57:36.000000000 +0100
+++ pdftk-1.45-dist/pdftk/Makefile.Base	2013-03-24 18:32:52.669492230 +0100
@@ -44,7 +44,7 @@
 	$(CXX) $(CPPFLAGS) $(CXXFLAGS) -I$(JAVALIBPATH) pdftk.cc -c
 
 pdftk : pdftk.o attachments.o report.o $(JAVALIB) $(GCJ_LOCAL_LIB_FULL)
-	$(CXX) $(CXXFLAGS) attachments.o report.o pdftk.o $(JAVALIB) $(GCJ_LOCAL_LIB_FULL) $(LDLIBS) -o pdftk
+	$(CXX) $(LDFLAGS) $(CXXFLAGS) attachments.o report.o pdftk.o $(JAVALIB) $(GCJ_LOCAL_LIB_FULL) $(LDLIBS) -o pdftk
 
 install:
 	/usr/bin/install pdftk /usr/local/bin 
diff -ruN pdftk-1.45-dist.orig/pdftk/Makefile.Debian pdftk-1.45-dist/pdftk/Makefile.Debian
--- pdftk-1.45-dist.orig/pdftk/Makefile.Debian	2012-12-06 19:58:44.000000000 +0100
+++ pdftk-1.45-dist/pdftk/Makefile.Debian	2013-03-24 18:34:39.034540850 +0100
@@ -29,7 +29,7 @@
 # tools
 # need direct path to libgcj for gcjh (starting in gcj 4.1.2 per Aurélien GÉRÔME)
 TOOLPATH=
-export VERSUFF=-4.6
+export VERSUFF=
 export CXX= $(TOOLPATH)g++$(VERSUFF)
 export GCJ= $(TOOLPATH)gcj$(VERSUFF)
 export GCJH= $(TOOLPATH)gcjh$(VERSUFF)
@@ -71,13 +71,13 @@
 # only effects libraries following option on the command line
 #
 #  
-export CPPFLAGS= -DPATH_DELIM=0x2f -DASK_ABOUT_WARNINGS=false -DUNBLOCK_SIGNALS -fdollars-in-identifiers
-export CXXFLAGS= -Wall -Wextra -Weffc++ -O2
-export GCJFLAGS= -Wall -Wextra -fsource=1.3 -O2
-export GCJHFLAGS= -force
+export CPPFLAGS+= -DPATH_DELIM=0x2f -DASK_ABOUT_WARNINGS=false -DUNBLOCK_SIGNALS -fdollars-in-identifiers
+export CXXFLAGS+= -Wall -Wextra -Weffc++
+export GCJFLAGS+= -fsource=1.3
+export GCJHFLAGS+= -force
 export LDLIBS= -lgcj
 
 include Makefile.Base
 
 # required packages (xubuntu 12.04)
-# gcj-jdk, g++
\ Kein Zeilenumbruch am Dateiende.
+# gcj-jdk, g++