diff -Naur mupdf-1.13.0-source/Makefile mupdf-1.13.0-source.patched/Makefile
--- mupdf-1.13.0-source/Makefile	2018-04-12 09:14:06.000000000 -0400
+++ mupdf-1.13.0-source.patched/Makefile	2018-06-23 15:24:50.242018433 -0400
@@ -14,7 +14,7 @@
 # Do not specify CFLAGS or LIBS on the make invocation line - specify
 # XCFLAGS or XLIBS instead. Make ignores any lines in the makefile that
 # set a variable that was set on the command line.
-CFLAGS += $(XCFLAGS) -Iinclude
+CFLAGS += $(XCFLAGS) -Iinclude -fPIC
 LIBS += $(XLIBS) -lm
 
 LIBS += $(FREETYPE_LIBS)
@@ -325,10 +325,10 @@
 
 # --- Library ---
 
-MUPDF_LIB = $(OUT)/libmupdf.a
-THIRD_LIB = $(OUT)/libmupdfthird.a
-THREAD_LIB = $(OUT)/libmuthreads.a
-PKCS7_LIB = $(OUT)/libmupkcs7.a
+MUPDF_LIB = $(OUT)/libmupdf.so
+THIRD_LIB = $(OUT)/libmupdfthird.so
+THREAD_LIB = $(OUT)/libmuthreads.so
+PKCS7_LIB = $(OUT)/libmupkcs7.so
 
 MUPDF_OBJ := \
 	$(FITZ_OBJ) \
@@ -355,12 +355,16 @@
 	$(ZLIB_OBJ) \
 	$(LCMS2_OBJ)
 
-$(MUPDF_LIB) : $(MUPDF_OBJ)
+$(MUPDF_LIB) : $(MUPDF_OBJ) $(THIRD_LIB) $(THREAD_LIB)
+	$(LINK_CMD) -shared -Wl,-soname -Wl,libmupdf.so.$(SOMAJOR) -Wl,--no-undefined
 $(THIRD_LIB) : $(THIRD_OBJ)
+	$(LINK_CMD) -shared -Wl,-soname -Wl,libmupdfthird.so.$(SOMAJOR) -Wl,--no-undefined
 $(THREAD_LIB) : $(THREAD_OBJ)
+	$(LINK_CMD) -shared -Wl,-soname -Wl,libmuthreads.so.$(SOMAJOR) -Wl,--no-undefined -lpthread
 $(PKCS7_LIB) : $(PKCS7_OBJ)
+	$(LINK_CMD) -shared -Wl,-soname -Wl,libmupkcs7.so.$(SOMAJOR)
 
-INSTALL_LIBS := $(MUPDF_LIB) $(THIRD_LIB)
+INSTALL_LIBS := $(MUPDF_LIB) $(THIRD_LIB) $(THREAD_LIB) $(PKCS7_LIB)
 
 # --- Tools and Apps ---
 
@@ -444,6 +448,14 @@
 
 VERSION = $(shell git describe --tags)
 
+# 20180623 bkw: major/minor/micro versions for shared library.
+# SOMAJOR is the mupdf major/minor version jammed together (e.g. 113
+# for 1.13.0).
+# SOMINOR is the mupdf micro version (e.g. 0 for 1.13.0).
+SOMAJOR = $(shell echo $(VERSION) | cut -d. -f1-2 | sed 's,\.,,g' )
+SOMINOR = $(shell echo $(VERSION) | cut -d. -f3-  | sed 's,\.,,g' )
+SOVER = $(SOMAJOR).$(SOMINOR)
+
 version:
 	sed -i~ -e '/FZ_VERSION /s/".*"/"'$(VERSION)'"/' include/mupdf/fitz/version.h
 
@@ -482,7 +494,13 @@
 	install include/mupdf/pdf/*.h $(DESTDIR)$(incdir)/mupdf/pdf
 
 	install -d $(DESTDIR)$(libdir)
-	install $(INSTALL_LIBS) $(DESTDIR)$(libdir)
+	install -s -m0755 $(INSTALL_LIBS) $(DESTDIR)$(libdir)
+	( cd $(DESTDIR)$(libdir) ; \
+		for i in $(INSTALL_LIBS); do \
+			j=$$( basename $$i) ; \
+			mv $$j $$j.$(SOVER) ; \
+			ln -s $$j.$(SOVER) $$j ; \
+		done )
 
 	install -d $(DESTDIR)$(bindir)
 	install $(INSTALL_APPS) $(DESTDIR)$(bindir)