Wrong версия after compilation and installation of qpdf

I tried to install qpdf 5.1.3; the default one is 5.1.1 (I have Ubuntu 14.04).

After compiling it from the sourceforge download, версия 5.1.1 is installed. The output of /usr/local/bin/qpdf --version is:

qpdf version 5.1.1  
Copyright (c) 2005-2015 Jay Berkenbilt  
This software may be distributed under the terms of version 2 of the
Artistic License which may be found in the source distribution. It is
provided "as is" without express or implied warranty.

The output of apt-cache policy qpdf

qpdf:
Installed: 5.1.3-1
Candidate: 5.1.3-1
Version table:
*** 5.1.3-1 0
100 /var/lib/dpkg/status
5.1.1-1 0
500 fr.archive.ubuntu.com/ubuntu trusty/main amd64 Packages

It's confusing, and if I run

find . -type f -name 'qpdf' -exec {} --version \;

in the source folder I get

qpdf version 5.1.1  
Copyright (c) 2005-2015 Jay Berkenbilt  
This software may be distributed under the terms of version 2 of the
Artistic License which may be found in the source distribution. It is
provided "as is" without express or implied warranty.  
qpdf version 5.1.3  
Copyright (c) 2005-2015 Jay Berkenbilt  
This software may be distributed under the terms of version 2 of the
Artistic License which may be found in the source distribution. It is
provided "as is" without express or implied warranty.

so there seems to be two versions compiled.

What's wrong here?